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Talk:Phonon

Colors of graphs
Some colors are not easy to distinguish (especially shades of red/green). Please use proper and clear contrast that avoids doubt over "pretty" or fashionable colors.

On 1D normal mode
I think the simulation on 1D phonon is very helpful for beginner to have a better understanding of lattice waves. It would be better if the author can clarify that the mode depicted is a longitudinal mode. Also, is the simulation depicting mono-atomic crystal or diatomic crystal? It seems that sometimes the "atoms" come too close to one another, which does not happen in real systems because of strong repulsion between atoms when they are less than one atomic diameter apart.WingkeeLEE 02:13, 22 June 2007 (UTC)

It is interesting to note that the most highly electrical conductive elements are those with an odd Z atomic number, which might imply the ability of interatomic agitation to aid in the electron transfer process. For example, it's easy to rub an electric charge off of sulfur, but the accumulated material is also a very good insulator.WFPM (talk) 17:18, 26 April 2010 (UTC)

 * Odd electrons per unit cell means half full bands in band theory, which tends to make better conductors. Full bands don't contribute to conduction. Almost full bands contribute holes, for a positive Hall coefficient. Gah4 (talk) 07:47, 13 July 2019 (UTC)

Oversized .GIF
Anyone else annoyed by the 6mb animated GIF? While it is effective at demonstrating a point, isn't there something that can be done about such a massive bandwidth hog? 60.224.44.222 08:08, 19 August 2006 (UTC) (can't be bothered signing in)

 * To Canberra-based user in Australia who "can't be bothered" to sign in: (a not-too-effective way to get people interested in queueing up behind you on an issue). Anyway, no kidding on the 6 MB file size! I didn't want to visit this article or even link to it because it was so damn slow. Now fixed.  I used two applications on a Mac to convert the file into a version that is 4.7% the size of the original, is indistinguishable from the original in visual appearance, and which loads much faster. This version also has an interframe delay of 40 ms (v.s. the original’s 100 ms).  Including processing time for each frame, this new version advances from frame to frame in 45–50 ms (a frame rate of about 20–22.5 Hz on a typical computer), which yields a more fluid motion.   Greg L 14:28, 4 October 2006 (UTC)

 * I have only a general familiarity with solid state physics, but I think that the diagram could be clarified by identifying the variables omega, lambda, and a. I see down in the article that a refers to lattice spacing, and I assume omega has something to do with frequency, but because these variables are only 'semi-standard' within physics, I'd like whoever posted the gif to either explain what the variables are within the caption, or, tell me so I can add a couple of sentences identifying the variables. I think that's just good diagramming-etiquette.
 * Trumpetmeister 14:57, 29 March 2008 (UTC)

Is this an error?
"There is no energy gap for phonons" (under Dispersion Relation) - but then what about Phononic Crystals which do have energy gaps? - h2g2bob 11/11/05

 * I suspect you'll find they're photonic crystals... -- CYD

 * There are both, though phononic and photonic crystals are very similar (phononic crystals have gaps in the acoustic (long wavelength) dispersion curve I believe) - h2g2bob 12/11/05

You should also note that several devices have gaps within there phonon spectrums such as silicon nanowires and nanodots (See Applied Physics Letters, Volume 87, Article) ) - shepplestone 4-6-06

Having researched and examined the topic further, I have deleted the above statement as it is incorrect. shepplestone.

Please elaborate
I have read this article a few times and still only have a vague concept of phonons. Can we get some more detail (and layman's explanations) on these sections:

"According to a well-known result in classical mechanics, any vibration of a lattice can be decomposed into a superposition of normal modes of vibration."

Can we link to an article about this rule, or give a short explanation if none exist?

"Secondly, we treat the potentials V as harmonic potentials, which is permissible as long as the atoms remain close to their equilibrium positions. (Formally, this is done by Taylor expanding V about its equilibrium value.)"

The link to screened in the sentence above this one helps explain it, but the link to harmonic oscillator doesn't really explain to me what a "harmonic potential" is.

"As we shall see in the following sections, any wavelength shorter than this can be mapped onto a wavelength longer than a."

This seems similar to aliasing in discrete-time sampled signal processing. If the analogy is close enough, should it be mentioned? Also, analogies to vibrations in strings would help me in particular, but I don't know how close these analogies are, and if they would give the wrong idea.

I guess the rest I don't understand simply because I don't know quantum mechanics... - Omegatron 14:26, Jul 21, 2004 (UTC)

 * I think some of these have been addressed, but the entry definitly still needs some work (I'll see what I can do ;-). I like the aliasing analogy, it's exactly right (the points where the atoms are placed act like the points (in time) where the analogue wave is detected in digital streams.) --H2g2bob 02:10, 16 December 2005 (UTC)

--- Would it be possible to add some stuff about non-equilibrium processes, like thermal conductivity??

Thermal conductivity has a seperate page within wiki

correcting small erro
Shouldn't "k" be "k_sub_n" in the exponents of the two Fourier relations immediately following the "One-Dimensional Phonons" subheading? Marcusl 15:58, 15 February 2006 (UTC)

Phonons & sound
In my opinion the reference to the name of Phonons is wrong: Phonons do not give rise to sound in crystals, there is merely a resemblace in the process. Sound would assume frequencies at least remotely near the audable range, which is not the case with phonons (>8 orders of magnitude difference).
 * Phonons do indeed give rise to sound in crystals. Although the order of magnitude of the frequency for phonons is typically given in the terahertz, this is for shorter wavelengths near the Brillouin zone edge.  In the long wavelength limit, the dispersion relation for the acoustic phonon branch becomes linear.  The slope of the dispersion relation in the long wavelength limit is the speed of sound in the crystal.UrbanaAchiever 01:48, 5 June 2007 (UTC)
 * Well, first, we most often think of sound propagating in gases, but it also goes through liquids and solids. And once you have the physics of it propagating through solids, it is the same physics at low and high frequency. The velocity is much higher in solids, so you would need a really big crystal to get down to audible frequencies. The physics would be the same, though. Phonon is mostly used when quantum effects are important, which is low temperatures (when the more random effects die down). Gah4 (talk) 14:46, 21 June 2021 (UTC)
 * Well, first, we most often think of sound propagating in gases, but it also goes through liquids and solids. And once you have the physics of it propagating through solids, it is the same physics at low and high frequency. The velocity is much higher in solids, so you would need a really big crystal to get down to audible frequencies. The physics would be the same, though. Phonon is mostly used when quantum effects are important, which is low temperatures (when the more random effects die down). Gah4 (talk) 14:46, 21 June 2021 (UTC)
 * Well, first, we most often think of sound propagating in gases, but it also goes through liquids and solids. And once you have the physics of it propagating through solids, it is the same physics at low and high frequency. The velocity is much higher in solids, so you would need a really big crystal to get down to audible frequencies. The physics would be the same, though. Phonon is mostly used when quantum effects are important, which is low temperatures (when the more random effects die down). Gah4 (talk) 14:46, 21 June 2021 (UTC)

Billiard ball model of the atmosphere
If one models air and air molecules as a lot of billiard balls in constant chaotic motion, then how does sound propagate through air? Are phonons associated with nitrogen and oxygen molecules, as they are with metal molecules? It seems it would be sort of Rube Goldbergian (like the board game Mousetrap) for sound to be carried and transferred between so many billiard balls in constant chaotic motion, when one is speaking to someone across the room.

I have read that air molecules at room temperature move about as fast as a jetliner; and that the average path lenght of an air molecule at room temperature is less than a meter. User: McTrixie --71.124.219.87 17:20, 27 August 2006 (UTC)

Some of them do move as fast as a jetliner, but some do not. They are distributed on a well known function called the "Maxwell–Boltzmann distribution". Sound is a statistical phenominon, because of the great many molecules involved, and hence behaves very well, even though each individual molecule seems to be very incapable of transmiting sound. On the whole, the millions and billions of molecules manage it collectivly.

Why?
It's easy to think of waves in a lattice, but I still don't see why they would qualify as a (quasi)particle. Presumably physicists invented/discovered phonons because they are a useful description of the world, but when do they behave like particles? —Ben FrantzDale 06:05, 19 January 2007 (UTC)

 * For instance in inelastic scattering experiments (Brilloiun scattering, Raman scattering, neutron scattering etc.) they behve like particles. User:Matthias_Buchmeier

 * This is similar to the question of describing light as an electromagnetic wave or as a stream of photons. At lower frequencies, the wave description works best, at higher frequencies particles. Gah4 (talk) 07:54, 13 July 2019 (UTC)

Phonons = bosons?
Hello,

This article seemingly contradicts boson by stating that phonons are bosons with integer spin, whilst the boson article states that bosons are particles with integer spin. This would make phonons=bosons, where my understanding of phonons is that they are purely propagation modes, where bosons are actual particles (where the word particle makes sense in quanta.

My understanding is insuffificent to declare this as correct, but does anyone have a definitive answer? User A1 14:08, 29 January 2007 (UTC)

 * anything with integer spin is in a group called the boson's, anything with half integer spin is in a group called hadron's, hence everything is either a boson or a hadron, in quantum mechanics ANYTHING with energy is a wave and so has a frequency and everything with frequency is a particle. so people are hadronic particles! the simplest observable indication of which of these groups something is in comes from the fact that hadrons can't pass through each other, when bosons can, since classical waves, like vibration, can, they are always bosons.

Asplace 11:19, 2 February 2007 (UTC)

 * So would I be correct in saying that the integer spin comment in phonon is superfluous? User A1 14:07, 2 February 2007 (UTC)

 * well you could actually read that last sentence in the header as, phonons are bosons BECAUSE they have integer spin. which is the definition of a boson, but seems to me ok if you assume the reader needs to be told that.
 * However i'm not sure the whole of the second paragraph isn't redundant, its trying to explain some general principles of QM, not really specific to phonons, a reader might be better of clicking the link to quanta at the top and reading about QM/superposition etc. there. this description is not the clearest i've come across. For example "they acquire certain particle-like properties when the lattice is analysed using quantum mechanics" how can an analysis cause properties? QM came about because people were already seeing particular properties in waves and needed to explain them, put simply, QM invents the concept of a wave/particle and says every wave and every particle is one of these, and it was a mistake to ever of thought they weren't. of course the maths used before QM doesn't suddenly stop working, but has clearer applicability restrictions.
 * Asplace 17:12, 2 February 2007 (UTC)

Re: Asplace who says anything with half-integer spin is a hadron. THIS IS INCORRECT. A hadron is a particle that can interact via the Strong interaction. You can have hadronic bosons (mesons). A FERMION is a particle with half-integer spin. Hadronic fermions are called baryons. Therefore all particles are either bosons or fermions, and may or may not also be a hadron. An example of a half-integer spin particle that is not a hadron is the electron. Such non-hadronic fermions are called leptons.86.133.152.185 13:33, 24 May 2007 (UTC)

Phasons?
I hoped to find here something about phasons which apparently are a special case of phonons existing in more complicated (e.g. incommensurate) structures. At a recent discussion on quasicrystals they were descibed as a misunderstanding, with the suggestion that 'phason' is in fact an adjective (and thus 'phasonic' is a pleonasm). Perhaps phasons should be mentioned briefly here and linked to separate article that somebody will write.195.96.229.83 10:12, 23 February 2007 (UTC)

Different masses?
¿why always the masses are the same in the solution of phonons? In many systems, the masses are not ordered neither the same.

The mass used is that of the crystalline unit cell which will always be the same. If the masses are not ordered you do not technically have a phonon since the whole concept is dependent on the existence of a perfectly ordered unit cell periodic in all directions. —Preceding unsigned comment added by 24.30.105.9 (talk) 07:45, 15 November 2007 (UTC)

Hermitian
Would standing waves be Hermitian ? Is this article supposed to be in sync with the French one? Arnero 05:55, 1 September 2007 (UTC)

Diagram in dispersion relation
In the dispersion relation section there is talk of a diagram, however I don't find it depicted in the article. I think including it would be very helpful in better understanding the section. —Preceding unsigned comment added by 86.198.1.156 (talk) 07:53, 30 October 2007 (UTC)

Still not fixed. "The blue, violet, and brown curves are those [...]" If nobody rectifies this in the next few days, I'll go ahead and remove the diagram references myself. 86.143.122.161 (talk) 12:37, 30 December 2007 (UTC)

The references are still there. In my opinion, one should not simply remove them. Instead, the missing diagram should be added or, to avoid clutter, an article that has a similar diagram must be linked here. So far, I have not been able to find such article. I think I could draw the diagram myself, but I am not familiar enough with the subject to explain it as clearly as this article needs. 82.147.167.179 (talk) 13:24, 13 January 2009 (UTC)

Can somebody fix some curves please? 87.64.35.12 (talk) 08:34, 25 May 2010 (UTC)

It would be nice if someone made said diagram. The issue was addressed as early as 2007, so may I ask why no-one has fixed it since? --Korot (talk) 20:03, 5 February 2011 (UTC)

Total Rewrite ?
My understanding is that an Wikipedia article ought to be readable by the average person, say, a high school student. I am a scientist and at 10 am, with no coffee in me, I can't read this article.Cyclopiano (talk) 18:19, 29 January 2008 (UTC)

 * I agree - the article needs to be made more accessible, at least to someone familiar with similar theory of light. HiraV (talk) 15:02, 16 November 2009 (UTC)

 * I agree too... the content of this article seems to me the material for a manual (wikibooks?) rather than an encyclopaedia (p.s. the lack of caffeine in a physicists blood stream at 10am does not support the validity of your comment though :)) Profeta (talk) 17:09, 20 April 2010 (UTC)

 * If people do a rewrite, I sure hope this article (or something quite like it) remains conveniently available. I also suggest that it remain editable like a Wikipedia article.  Phonons just aren't simple.  The article does give me a rough intuitive sense of what phonons are, which is an achievement.  But I don't claim to understand very much of the article, and my background isn't typical for Wikipedians.  Several decades ago, I passed a course in mineralogy (for geologists) and a 1-quarter introduction to quantum mechanics.  So, long ago, I heard about Hamiltonians, even though I've never done anything with them since then.  I got to the article from the article on cristobalite, about which I learned a little bit, decades ago.  Oaklandguy (talk) 22:58, 1 February 2014 (UTC)
 * I'm a scientifically literate lay person, and I find the article incomprehensible. The theory and detail in the article is useful for those that can make sense of it, but it needs an expanded lead and an overview section that explains the concept without jargon or mathematics. WP is an encyclopedia, not a textbook. --Ef80 (talk) 20:28, 2 July 2016 (UTC)
 * I suppose so, but it is mostly quantum mechanics. According to Feynman (who got a Nobel prize doing it), "Nobody understands quantum mechanics", so I am not sure we can expect high school students to understand it. High school students are expected to believe in, and sort-of understand, photons. That light is made up of particles that travel though vacuum or many materials, even without really understanding electromagnetism or Maxwell's equations. But vibrations are something we think we understand, and especially their non-quantum properties. Photons tell us that there is a smallest amount of light that we can have, at a give frequency. Phonons tell us that there is a smallest amount of vibration we can have, at a give frequency. Somehow, though, since we find vibration more understandable, quantization of it is less understandable. Gah4 (talk) 14:57, 21 June 2021 (UTC)
 * I suppose so, but it is mostly quantum mechanics. According to Feynman (who got a Nobel prize doing it), "Nobody understands quantum mechanics", so I am not sure we can expect high school students to understand it. High school students are expected to believe in, and sort-of understand, photons. That light is made up of particles that travel though vacuum or many materials, even without really understanding electromagnetism or Maxwell's equations. But vibrations are something we think we understand, and especially their non-quantum properties. Photons tell us that there is a smallest amount of light that we can have, at a give frequency. Phonons tell us that there is a smallest amount of vibration we can have, at a give frequency. Somehow, though, since we find vibration more understandable, quantization of it is less understandable. Gah4 (talk) 14:57, 21 June 2021 (UTC)
 * I suppose so, but it is mostly quantum mechanics. According to Feynman (who got a Nobel prize doing it), "Nobody understands quantum mechanics", so I am not sure we can expect high school students to understand it. High school students are expected to believe in, and sort-of understand, photons. That light is made up of particles that travel though vacuum or many materials, even without really understanding electromagnetism or Maxwell's equations. But vibrations are something we think we understand, and especially their non-quantum properties. Photons tell us that there is a smallest amount of light that we can have, at a give frequency. Phonons tell us that there is a smallest amount of vibration we can have, at a give frequency. Somehow, though, since we find vibration more understandable, quantization of it is less understandable. Gah4 (talk) 14:57, 21 June 2021 (UTC)

link to insulating solids
Should the link "insulating solids" in the first paragraph be to electrical insulation rather than thermal insulation? Igwood (talk) 04:26, 23 November 2008 (UTC)
 * Seems to have been changed to link to both. Do note, though, that heat travels through electrical conductors (metals) better than non-metals, and for good reasons. In any case, both are important, and especially when considering phonons. Gah4 (talk) 15:01, 21 June 2021 (UTC)
 * Seems to have been changed to link to both. Do note, though, that heat travels through electrical conductors (metals) better than non-metals, and for good reasons. In any case, both are important, and especially when considering phonons. Gah4 (talk) 15:01, 21 June 2021 (UTC)

Relation to photons?
Is not heat electromagnetic energy? Then, wouldn't that mean that all phonons are photons? I mean if we are talking about heat, and phonons are the particles of heat, then wherever there are photons there are phonons. Tcaudilllg (talk) 08:11, 9 February 2009 (UTC)
 * In short: no - heat is not electromagnetic energy. Read the Heat article for details, but in summary: heat may describe the energy transferred between objects at different temperatures (by any mechanism, of which electromagnetic radiation is but one), or, less formally, the energy "in" an object contributing to its temperature (e.g. the kinetic energy of its component particles). Phonons are (modes of) physical vibration in a regular lattice of particles (i.e. they are MECHANICAL vibrations, not electromagnetic vibrations). Phonons, being mechanical vibrations, carry energy, and so can transport energy; in this context they might be described as "particles of heat", but in that case there are several quite different kinds of "particles of heat" (e.g. photons; individual atoms / ions; individual sub-atomic particles; gravitons ...).FredV (talk) 14:15, 27 July 2009 (UTC)
 * It is more complicated than that, but the answer is still no. Photons are the carrier of the electromagnetic force, and so are responsible for holding molecules and crystals together. However, radiant heat, mostly far-IR, is photons. Convection is motion of different molecules in a gas or liquid. Conduction of heat is mostly phonons. Energy can exchange between the different types, and usually does. Consider a nitrogen molecule in the air, spinning around with thermal energy. We tend to think that things can spin at any rate we want them to, but no. Molecular rotation is quantized, such that they can only spin at certain speeds. At low temperature, there is a slowest speed that they can spin. However, polarized molecules will couple to the electromagnetic field, and so photons. You can't get away from either of them.Gah4 (talk) 15:14, 21 June 2021 (UTC)
 * It is more complicated than that, but the answer is still no. Photons are the carrier of the electromagnetic force, and so are responsible for holding molecules and crystals together. However, radiant heat, mostly far-IR, is photons. Convection is motion of different molecules in a gas or liquid. Conduction of heat is mostly phonons. Energy can exchange between the different types, and usually does. Consider a nitrogen molecule in the air, spinning around with thermal energy. We tend to think that things can spin at any rate we want them to, but no. Molecular rotation is quantized, such that they can only spin at certain speeds. At low temperature, there is a slowest speed that they can spin. However, polarized molecules will couple to the electromagnetic field, and so photons. You can't get away from either of them.Gah4 (talk) 15:14, 21 June 2021 (UTC)
 * It is more complicated than that, but the answer is still no. Photons are the carrier of the electromagnetic force, and so are responsible for holding molecules and crystals together. However, radiant heat, mostly far-IR, is photons. Convection is motion of different molecules in a gas or liquid. Conduction of heat is mostly phonons. Energy can exchange between the different types, and usually does. Consider a nitrogen molecule in the air, spinning around with thermal energy. We tend to think that things can spin at any rate we want them to, but no. Molecular rotation is quantized, such that they can only spin at certain speeds. At low temperature, there is a slowest speed that they can spin. However, polarized molecules will couple to the electromagnetic field, and so photons. You can't get away from either of them.Gah4 (talk) 15:14, 21 June 2021 (UTC)

Vandalism
Someone did a search-and-replace and replaced all instances of 'phonon' with 'photon', both in the article and the discussion page. I have fixed this. Nightrose (talk) 23:47, 10 June 2009 (UTC)

Quantisation
The explanation of quantisation of wavelength for phonons arising because of the lattice spacing seems simple enough, but I can't understand why this necessarily leads to quantisation of phonon energy. Why can a phonon of a given wavelength not take on a range of amplitudes (and hence a range of energies)? Andipi (talk) 11:50, 16 August 2009 (UTC)

 * E=hf and so E=hc/lambda as c=f*lambda, hence the energy is constant for each given wavelength. HiraV (talk) 15:02, 16 November 2009 (UTC)

 * I had exactly the same question and after reading (what I could of) the article was starting to think energy wasn't quantised at all for phonons, which seemed pointless. Not until I got here did it make any sense. I agree with your comment below - the opening leads the reader down the wrong path and I think it needs to be improved (I would say "fixed" but the whole crystal lattice and diagram thing made sense to me).--Adx (talk) 09:38, 1 June 2010 (UTC)

 * Increased amplitude mean more phonons in the same quantum state. (Remember, they are bosons.) As usual for QM descriptions, macroscopic sized objects have very large N (number of atoms, and so possible modes), and at normal temperatures, the modes are well populated. The quantum steps are small enough to look continuous. At low temperatures, quantum effects are more visible. Gah4 (talk) 08:05, 13 July 2019 (UTC)

Definition
I think the page should be started differently; phonons are defined not as the modes of vibration but the quanta of energy that these modes carry - this may lead to confusion. Phonons are to lattice vibration as photons are to electromagnetic radiation - individual fundamental quanta of energy. Should I change the opening of the page? HiraV (talk) 15:02, 16 November 2009 (UTC)

No Merger from Light scattering
I do not support the suggestion that the discussion of lattice vibrations and light scattering should be transferred to this general page on the description and mathematics of phonons. The brief description of thermal motion in elastic solids is essential there in order to develop a complete understanding of the mechanisms of Brillouin scattering (& sound absorption) by density fluctuations and microstructural defects in condensed matter. As pointed out there, light scattering has made possible the study of molecular processes from time intervals as short as 10−11 sec. This is one particular application amongst a number of subjects related to phonon transport.

Thus, there is no reason to support this merger. Rather, the main page on phonons should be clearly referenced there. logger9 (talk) 04:20, 25 June 2010 (UTC)

An error: the momentum is not k=πnj/Na but k=2πnj/Na
An error: the momentum is not k=πnj/Na but k=2πnj/Na

Read any book of quantum chain please. — Preceding unsigned comment added by 82.139.116.215 (talk) 00:55, 20 October 2011 (UTC)
 * To explain more explicitly, the periodic boundary condition requires x_N+1 = x+1. Allowing k to be odd multiples of πnj/Na violates this condition.  Physically, the longest possible wavelength is the length of the chain, Na.  It looks like the previous treatment was done with non-periodic boundary conditions, despite the text's claim to the contrary.  Correcting k=πnj/Na to k=2πnj/Na left some inconsistencies in the limits on both the sums in x_j / p_j and the allowed values for n, which I have corrected.  I admit that summing from -N/2 to +N/2 makes for an ugly formula (which is why I removed the \matrix formatting, it was getting very crowded).  Going from 0 to N would be equivalent, but I think using the symmetric interval is a more intuitive representation of left- and right-traveling waves.  — Preceding unsigned comment added by 128.205.65.123 (talk) 00:51, 26 October 2011 (UTC)
 * This is reminding me of the difference between the Fourier (exponential) transform and the Fourier cosine transform. More specifically (in the case of crystals) DFT vs. DCT. The boundary conditions are different, and in the case of DCT, the lowest wavelength is twice as long. Periodic boundary conditions are nice, as you don't have to worry about surface effects. Gah4 (talk) 15:22, 21 June 2021 (UTC)
 * This is reminding me of the difference between the Fourier (exponential) transform and the Fourier cosine transform. More specifically (in the case of crystals) DFT vs. DCT. The boundary conditions are different, and in the case of DCT, the lowest wavelength is twice as long. Periodic boundary conditions are nice, as you don't have to worry about surface effects. Gah4 (talk) 15:22, 21 June 2021 (UTC)
 * This is reminding me of the difference between the Fourier (exponential) transform and the Fourier cosine transform. More specifically (in the case of crystals) DFT vs. DCT. The boundary conditions are different, and in the case of DCT, the lowest wavelength is twice as long. Periodic boundary conditions are nice, as you don't have to worry about surface effects. Gah4 (talk) 15:22, 21 June 2021 (UTC)

Interpretation of phonons using second quantization techniques
An edit on September 22 by user Cesaranieto (see copied details below) seem to have made a large difference to this section of the article. For example, the user added new/extra notation including $$l_k = \sqrt{\hbar/m\omega_k}$$, that is not at all necessary and changed the operators from a's to b's for no obvious reason. The most troubling change though is the definition of the ladder operators. I have worked out the commutation relation for the operators as defined and it does not give the correct value. With the old definition of the a's, the commutation does work out correctly such that $$[a_k, a_k^{\dagger}] = 1$$. Of course, it is possible that I made a mistake, and I have been unable to find a suitable primary source containing the answer. Nonetheless, unless someone can explain why the change was made, I will revert to the original version tomorrow.

The offending change (if I judge correctly, my mediawiki-fu is not too strong) 22:58, 22 September 2012 Cesaranieto (talk | contribs). . (34,165 bytes) (+173)

Micah Stoutimore (talk) 01:01, 16 October 2012 (UTC)

phonons and vibrations, quanta and waves
A lot of the results on this page (animations, dispersion relations) seem to have to do with lattice vibrations in general. I think it might be nice to have a separate article that discusses lattice vibrations in general (acoustic vs optical vibrations, Brilloin zones, dispersion etc.), so that the phonon article can deal with issues that specifically involve the quantization of lattice vibrations. This would be analogous to how there are separate pages for electromagnetic radiation and photon. Nanite (talk) 13:36, 29 January 2014 (UTC)
 * I agree, it will be great for the readability of both articles and make it easier to structure all the information. JanJaeken (talk) 10:11, 30 January 2014 (UTC)

LO vs TO vs LA vs TA
It would be nice if this article could have more information explaining how to distinguish these types of modes when looking at a phonon dispersion spetra. For instance I've been told that acoustic modes always start at zero frequency at k=0 due to Bose symetry. Also there is typically LO-TO splitting so the TO mode is at lower frequency (in salts, one can prove the LST relation). I've been told LO modes typically have a larger slope than TO modes. It's hard to find reference that prove these points hold in general, though. I've heard a good reference is "electrons and phonons" by Ziman, but I don't have access to it at the moment. Danski14(talk) 22:10, 23 February 2015 (UTC)

Not quasiparticles?
I don't understand what this means: Even though phonons are often used as a quasiparticle, some popular research has shown that phonons and rotons may indeed have some kind of mass and be affected by gravity 1. What does "often used as" mean? Are they quasiparticles or not? As I understand the rest of the article, a phonon is a quasiparticle by definition, and nobody has suggested they are physical particles. 2. The sentence seems to imply that quasiparticles having mass is a contradiction. But the second sentence of the quasiparticle article mentions the example of an electron in a semiconductor that acts like a quasi-electron with different mass. So evidently the notion that quasiparticles cannot exhibit mass is erroneous. It wouldn't make sense to speak of quasiparticles if they didn't exhibit measurable physical properties such as mass.--85.247.151.151 (talk) 12:08, 12 March 2019 (UTC)
 * I agree with you and will remove the offending statement. The cited reference makes no attempt to say it is not a quasi-particle, it does not even mention quasiparticles in any context. Additionally, as you point out, that is misusing the term quasiparticle. A quasiparticle is any particle that does not share all characteristics shared by the underlying particle. An electron with a slightly different mass or charge would be a quasiparticle, an electron with no mass is also a quasiparticle, which does make sense and is useful at times in HEP. Footlessmouse (talk) 23:45, 14 August 2020 (UTC)
 * I suppose, but if you try too hard, I suspect everything in quantum mechanics is a quasiparticle, so they might as well just all be particles. That is, in wave-particle duality, we don't say wave-quasiparticle duality. Are photons quasiparticles? Otherwise, it is a reminder not to look too closely. Since phonons have enegy, and energy is equivalent to mass, I suspect that means that they have gravitational mass, not that you could measure it. Gah4 (talk) 14:12, 1 May 2022 (UTC)
 * I suppose, but if you try too hard, I suspect everything in quantum mechanics is a quasiparticle, so they might as well just all be particles. That is, in wave-particle duality, we don't say wave-quasiparticle duality. Are photons quasiparticles? Otherwise, it is a reminder not to look too closely. Since phonons have enegy, and energy is equivalent to mass, I suspect that means that they have gravitational mass, not that you could measure it. Gah4 (talk) 14:12, 1 May 2022 (UTC)
 * I suppose, but if you try too hard, I suspect everything in quantum mechanics is a quasiparticle, so they might as well just all be particles. That is, in wave-particle duality, we don't say wave-quasiparticle duality. Are photons quasiparticles? Otherwise, it is a reminder not to look too closely. Since phonons have enegy, and energy is equivalent to mass, I suspect that means that they have gravitational mass, not that you could measure it. Gah4 (talk) 14:12, 1 May 2022 (UTC)

second quantization
There are many in the second quantization section, pretty much on each equation. As well as I know, it is described in most upper level undergraduate, and many graduate level QM books. I suppose we could specify one, but if most have it, it shouldn't be needed. Gah4 (talk) 08:10, 13 July 2019 (UTC)

I will write out proofs for these equations and remove the citation needed templates. If any other editors disapprove of this, I can just add an arbitrary reference to Griffiths or something (I will double check to make sure it has the info, of course, but Gah4 is correct, this is basic content found in most undergrad textbooks on the topic). Let me know what you think. Footlessmouse (talk) 00:04, 15 August 2020 (UTC)

The use of the term ladder operators in this section differs in terminology from creation and annihilation operators used elsewhere. I have rewritten a chunk of this section already, but left this quirk, should we make it consistent, or point out they are the same thing? Footlessmouse (talk) 07:41, 15 August 2020 (UTC)
 * As well as I know it, ladder operators is the collective term for both, as they walk up or down the ladder of states. Shorter than saying creation and annihilation operators every time. Gah4 (talk) 14:06, 1 May 2022 (UTC)
 * As well as I know it, ladder operators is the collective term for both, as they walk up or down the ladder of states. Shorter than saying creation and annihilation operators every time. Gah4 (talk) 14:06, 1 May 2022 (UTC)

Reference to first mention considered
A recent article mentions “First proposed by Albert Einstein in 1907, phonons are packets of vibrational energy emitted by jittery atoms.” which seems to contradict or at least require an additional citation on the origin of phonons.

Article on recent advancements using phonons as a microphone which includes the mention of Einstein: https://m.phys.org/news/2019-07-physicists-particles-quantum-microphone.html

I have not researched this claim but opening up discussion on future changes to this page. Listre (talk) 21:16, 29 July 2019 (UTC)

typo?
I cannot understand this sentence: "It is customary to deal with waves in Fourier space which uses normal modes of the wavevector as variables instead coordinates of particles."

Should be 'instead of coordinates'? — Preceding unsigned comment added by 76.169.229.184 (talk) 16:21, 20 June 2021 (UTC)
 * It still sounds a little strange. Fourier space means frequency space. (Or spatial frequency, as the case may be.) But yes, they should be considered as ω and k (wave vector or wave number), and not as position and velocity (or time). Gah4 (talk) 15:30, 21 June 2021 (UTC)
 * It still sounds a little strange. Fourier space means frequency space. (Or spatial frequency, as the case may be.) But yes, they should be considered as ω and k (wave vector or wave number), and not as position and velocity (or time). Gah4 (talk) 15:30, 21 June 2021 (UTC)

atoms or molecules uniformly oscillates at a single frequency
The article says: atoms or molecules uniformly oscillates at a single frequency. It seems to me that the usual uncertainty principle should apply, and like photons, be a wave packet with a width (in frequency) and length (in time). If the width is narrow compared to other scales in the problem, I suppose single frequency is a good approximation. But that mostly only works when there are a large number in a mode. That is, when the phonon (particle like) explanation isn't needed. Gah4 (talk) 10:35, 29 December 2021 (UTC)
 * Regarding a recent edit, I was going to say this, but it seems I said it last year. Gah4 (talk) 14:03, 1 May 2022 (UTC)
 * Regarding a recent edit, I was going to say this, but it seems I said it last year. Gah4 (talk) 14:03, 1 May 2022 (UTC)

"Phononic Computing" listed at Redirects for discussion
An editor has identified a potential problem with the redirect Phononic Computing and has thus listed it for discussion. This discussion will occur at Redirects for discussion/Log/2022 May 12 until a consensus is reached, and readers of this page are welcome to contribute to the discussion. 1234qwer1234qwer4 19:59, 12 May 2022 (UTC)

 * The field is just taking off. Why was it deleted from this article? https://phys.org/news/2019-05-phonon-mediated-quantum-state-remote-qubit.html Hcobb (talk) 20:33, 12 May 2022 (UTC)

single phonon detection
A recent edit indicates that single phonons are not detectable, but a web search finds many papers on them. It is convenient that many photons have energies that we can detect, especially in the visible optical range. Partly that is because a single molecule in our eye needs to detect one. But low energy photons are not individually detectable, such as those at radio frequencies. And for phonons, higher frequencies are individually detectable, and low frequency ones not detectable. Gah4 (talk) 05:36, 10 June 2023 (UTC)

Origin of the name
The introduction tells us, without citation, that the concept of phonons was introduced in 1932 by Soviet physicist Igor Tamm. Does anyone know which publication this refers to?

On the other hand, the book Twentieth century physics, Vol. I (p.1302) tells us that the name phonon was introduced by Frenkel in his 1932 book Wave mechanics: Elementary theory to ridicule the notion of a photon. If someone has access to that book, it would be interesting to know exactly what Frenkel writes on the subject. Jähmefyysikko (talk) 06:14, 10 June 2023 (UTC)

superconductivity
This article says

Phonons have also been predicted to play a key role in superconductivity in materials and the prediction of superconductive compounds

whereas Britannica says

''phonons are essential in the phenomenon of superconductivity... In superconducting metals at sufficiently low temperatures, however, electrons—which ordinarily repel each other—slightly attract each other through the intermediate effect of phonons. The result is that the electrons move through the material as a coherent group and no longer lose energy through individual collisions. Once this superconducting state has been achieved, any initial flow of electrical current will persist indefinitely.'' Espoo (talk) 06:09, 19 August 2023 (UTC)
 * BCS theory uses phonons in its explanation. Among others, the transition temperature, Tc, is dependent on the isotope mass, which couples to phonons. Gah4 (talk) 09:18, 28 February 2024 (UTC)
 * BCS theory uses phonons in its explanation. Among others, the transition temperature, Tc, is dependent on the isotope mass, which couples to phonons. Gah4 (talk) 09:18, 28 February 2024 (UTC)

Individual detection
I removed: However, photons are fundamental particles that can be individually detected, whereas phonons, being quasiparticles, are an emergent phenomenon. For those interested, the removed reference is here. Gah4 (talk) 09:05, 28 February 2024 (UTC)

title: Talk:Phonon


text:
VVT

VVT may refer to:

 * Valvettithurai, a town in Sri Lanka
 * Variable valve timing, an internal combustion engine valvetrain configuration
 * VVT (gang), a gang in Toronto, Canada

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: VVT


text:
Wikipedia:Featured article candidates/Plate tectonics/archive1

Plate tectonics
very good with nice images and lots of information Avala 19:51, 4 Jul 2004 (UTC)

 * Tentatively support. Well-written, but perhaps it could be longer - citing specific papers, people, &c. in the history section, perhaps? I'm not sure... Also, did plate tectonics actually contribute anything other than theoretical understanding, because, if it did, I didn't get such an impression from the article -- perhaps something on resultant predictions/findings, or theories based on this? James F. (talk) 20:27, 4 Jul 2004 (UTC)
 * This needs a list of the major plates in the article. Morwen - Talk 21:17, 4 Jul 2004 (UTC)
 * there is separated article- List of tectonic plates and List of tectonic plate interactions and List of plate tectonics topics
 * Yes. But that doesn't mean that info shouldn't be summarised in this article!  Morwen - Talk 21:49, 4 Jul 2004 (UTC)
 * Added this now. Morwen - Talk 20:51, 5 Jul 2004 (UTC)
 * why don`t you give a support now?Avala 21:06, 5 Jul 2004 (UTC)
 * It doesn't really matter whether she does or not, since the real question is whether anyone opposes. So long as she's withdrawn her objections, you're in the same position whether she supports or not. Snowspinner 14:45, Jul 6, 2004 (UTC)
 * (not a vote) Does the plate image really need to occur twice? Jeronimo 17:57, 5 Jul 2004 (UTC)
 * they are differenr
 * Umm, what? There are two images, one a map of the major plates, and one a diagrammatic over-view of subduction &c. James F. (talk) 19:13, 6 Jul 2004 (UTC)
 * Comment: Please edit the captions. See Captions. -- ke4roh 21:46, Jul 5, 2004 (UTC)
 * Support after recent changes. Anarion 08:40, 7 Jul 2004 (UTC)
 * Support without reservation. An excellent article, rendering a sometimes-thorny concept readily accessible to the interested layperson. Denni ☯ 22:27, 2004 Jul 11 (UTC)


text:
Pentwyn

Pentwyn (or Pen-twyn) may refer to the following places in south-east Wales:

 * Pentwyn, Cardiff, a district of the city of Cardiff
 * Pentwyn (electoral ward)
 * Pentwyn, Caerphilly, a village in the Darran Valley
 * Pen-twyn, Carmarthenshire, a hamlet near Cross Hands
 * Pentwyn, Focriw, a hamlet in Caerphilly, near Focriw
 * Pentwyn, Torfaen, a village near Abersychan
 * Pen-twyn, Trinant, a village in Caerphilly, near Trinant
 * Pentwyn Berthlwyd, a village in Merthyr Tydfil, near Treharris
 * Pentwyn Deintyr, village in Merthyr Tydfil
 * Pentwyn-mawr, village in Caerphilly, near Pontllanfraith

title: Pentwyn


text:
Lisvane

Lisvane (Llys-faen) is a community in the north of Cardiff, the capital of Wales, located 5 mi north of the city centre. Lisvane is generally considered to be one of the wealthiest residential areas of Wales, with many properties worth in excess of £1 million. Lisvane had 3,319 residents in 2001 and comprises approximately 1,700 dwellings, a local village shop, primary school, community cabin library, park, nursery, parish church, public house, war memorial, Scout hall and community or village hall.

Early history
The Welsh language name Llys-faen means 'Stone Court' (llys – court and faen/maen – stone). There have been several alternative spellings in the English language over the centuries such as Lysvayen, Lucyvene, Llisuine, Lyssefayn, Lysfayn, Lucyvine, Lucyvenye, Lucyveny, Leysvayen, Les Ffayne and Lliffeni. The village probably settled on the present name from around 1630. Each early Welsh kingdom was divided into lesser administrative units, cantrefs, which were further subdivided into cymydau (commotes). In each commote the royal taxation house was a large building made almost certainly of stone because it had to be permanent, weather proof and thief proof. The commote of Cibbwr/Kibbor was on land between Cefn Onn ridge and the coast and most historians agree that Llys-faen was its administrative centre, although Roath has also staked a claim. There is now no indication of the actual whereabouts of the Llys Faen or Stone Court, although various theories have been advanced.

The earthworks at Graig Llwyn is held to be the oldest artificial feature in Lisvane, proposed by several archaeologists to be the remains of an Iron Age stronghold. No definite date or purpose can yet be confirmed for this earthwork.

At the start of the 13th century the parish lands of Llanishen and Lisvane had been divided into Norman manors that were expected to provide food for the castle garrisoned at Cardiff. The southern facing slopes of the ridge above Lisvane with their rich agricultural land soon became the grain growing area for the supplies which were transported to Roath Mill for processing. There is a local legend that Oliver Cromwell once stayed at the Black Griffin Inn, prior to the Battle of St Fagans in May 1648 and that the Cromwell family once lived there briefly. There is no evidence to support this, though Cromwell must have lodged somewhere, but it is more likely that the Inn's only Cromwellian association is with soldiers of Cromwell's Model army. Cromwell was, however, of Welsh ancestry (his real name was Williams) and his great-grandfather came from this area.

The Tŷ Mawr
Tŷ Mawr is a historic house on the Graig slope overlooking the village. It was built as a farmhouse in the 18th to early 19th century and was in the estate of the Lewis family. In 1900 part of the estate was let to Lisvane Golf Club, who established a 9-hole course there but two years later, the club moved to Radyr, taking the clubhouse with them. From just after the Second World War, the fox hounds of the local Lisvane Hunt were kennelled at Tŷ Mawr until it became a public house in the 1960s.

The Llanishen and Lisvane Hunt had several homes over the years with the hunts most latterly setting off from Llan Farm on Graig Llwyn Road. The village hunt disbanded around 1997 on the death of the then hunt Master.

There is a local tradition that for a period during the 1800s, Erw-wen, on Rudry Road, was also a pub or beer house, possibly called the Red Cow, although no documentary proof has been found.

Lisvane and the Cold War
A few yards away from the Ordnance Survey's triangulation point on the Graig stands Lisvane's only Cold War nuclear bunker. During World War II the Royal Observer Corps (ROC) observation post stood on the Graig with its clear views over the village and the city of Cardiff. The volunteer ROC observers spotted many German Luftwaffe raids approaching across the channel and activated the air raid warnings in the Cardiff area. In early 1966 a protected nuclear fallout shelter (or bunker) was completed on the site for the ROC (OS Grid Ref: ST 1898 8508), who by the 1960s had switched from above ground aircraft spotting to underground operations with instruments to detect nuclear explosions and warn the public of approaching radioactive fallout in the event of nuclear war.

The only time post members had been mobilised and volunteers spent nearly ten days underground was during the Cuban Missile Crisis as the government prepared the country for potential outbreak of war. The Lisvane nuclear bunker was abandoned by the ROC in 1991 when the Corps itself was disbanded with the end of the Cold War and as a result of recommendations in the governments Options for Change review of UK defence. The Lisvane nuclear bunker still exists but it was purchased by a mobile phone communications company who built a radio mast inside the fenced compound and sited some of their equipment in the underground facility.

Notable domestic architecture

Several properties in Lisvane are listed for their historical and architectural significance by Cadw. Ty Gwyn on Lisvane Road was built as the personal residence of builder James E. Turner of E. Turner and Sons and is listed Grade II. The firm was responsible for much of the construction of Cardiff's Cathays Park civic centre. It was latterly the home of financier Julian Hodge. Lisvane House on Mill Road was built in the Arts and Crafts style by architect Edwin Seward. The Dingle is toward the upper end of Mill Road. It was designed by Percy Thomas, and is also listed Grade II.

Community Council
The village has an elected community council which is funded by a precept on council tax bills in the local area. It provides support to a number of community services. The council currently has ten councillors (9 Independent, 1 Conservative) with elections held every five years. The last election was held at the same time as the 2017 Cardiff Council election and the next election is due in May 2022.

Cardiff Council ward
Since 1999 the electoral ward of Lisvane has elected one councillor to Cardiff Council, namely David Walker for the Conservative Party. Before 1999, Lisvane was, with St Mellons and Pontprennau, part of the ward of Lisvane and St Mellons, which elected a single councillor to Cardiff Council. At the 1995 election, Lisvane and St Mellons was the only ward in Cardiff to elect a Conservative councillor. By 1999, the growth of Pontprennau led to the establishment of a separate ward of Pontprennau and Old St. Mellons, which elects two councillors, and Lisvane became a ward on its own.

The ward was bounded by those of Caerphilly county borough to the north; Pontprennau & Old St. Mellons to the east; Pentwyn to the southeast; Llanishen and Cyncoed to the south; and Rhiwbina to the west.

Following a boundary review and a projected population increase, the new community of Thornhill will be transferred from the Llanishen ward to Lisvane, effective from the 2022 Cardiff Council election. The ward will be renamed "Lisvane and Thornhill" and elect three councillors.

Senedd Cymru – Welsh Parliament
The Senedd representative for Cardiff North is Welsh Labour MS Julie Morgan.

Westminster
Lisvane lies within the parliamentary constituency of Cardiff North, which has been represented since 2017 by Anna McMorrin (Labour).

Geological structure
The surrounding soils are mostly a strong, brown, dry earth, well adapted for arable farming and the growing of grains of all kinds that contributed to the area being a mostly farming community until the modern era. Soils were further enriched over the millennia by alluvial deposits from the meandering River Taff and other smaller tributaries. The substratum under the whole area is a limestone and lime shale that was likely laid down under a warm ocean at some stage in the distant past and subsequently ground down by glaciers during the last ice age around 18,000 years ago.

M4 motorway
The neighbouring suburbs are Llanishen to the south, Thornhill to the west, Pontprennau to the east, and Lisvane's effective northern border is the M4 motorway. The M4 corridor around Cardiff was announced in 1971 as a replacement for a northern link road that had been on the statutes since 1947 but never built. The northern 'Lisvane route' for the M4 was eventually chosen after a number of public enquiries and objections from village residents. The new motorway was completed and opened in July 1980.

The Graig
The Graig is a hill situated north of Lisvane. It borders on Caerphilly. There is also a quarry near the Graig which is now abandoned. The Rhymney Valley Ridgeway Walk runs along the top of the Graig, and has some very good walks and mountain biking routes. Particular favourites for locals include routes to the east to Rudry and the Maenllwyd Inn, and to the west to Caerphilly mountain, The Travellers Rest, and further on to Tongwynlais, Castell Coch and the Taff Trail.

Demography
The United Kingdom Census 2011 demographically showed that the total population of Lisvane was 3,707. The average age was 44.6 years old and 69% of the adult population were married.

Of the 3,707 total, children under the age of 19 accounted for 864 and people over the age of sixty five totalled 866.

1,515 were in full-time employment, and 188 of those worked exclusively from home. Of those that travelled to their place of employment 1,090 drove by private car, 74 travelled by train and 43 by bus, 34 walked, 9 cycled and 77 travelled as passengers in other vehicles.

The white population accounted for 92.6% of the residents and of the remainder 4.2% were Asian, 0.5% Chinese, 1.5% were of mixed race and 0.2% were Black.

Economy
There are little in the way of major employers in the village. The area still has a predominantly farming economy. Some local employment is provided by the service industries of the shops and public houses. The general affluence in the village is mainly drawn from employment in the commerce and industry centre of the capital city. An increasing number of employees are working from home via high speed internet links and telephone.

Following improvements in the road and rail infrastructure some Lisvane residents commute daily to work in Bristol and London.

Landmarks

 * Parc Cefn Onn
 * The war memorial
 * St Denys Church
 * Graig Llwyn earthworks
 * The Graig Mountain
 * Lisvane Reservoir
 * Lisvane (CAC) Tennis Club

Education
Corpus Christi High School is the only secondary school located within Lisvane, just on its boundary with the ward of Cyncoed. However, school age residents fall into the catchment area for Llanishen High School in the ward of Llanishen, which is more accessible.

Llysfaen Primary School serves the local population of 4- to 11-year-olds.

Religion
St Denys' Church (Church in Wales) in the centre of the village was built in the 12th century and remodelled several times since. The listed building is notable for the imposing and unusual tower with a pitched roof but lacks the normal Norman castellations.

The first Baptist Chapel in Lisvane was built in 1789 on Chapel Road, now renamed Rudry Road, and only stood for less than thirty years until it had to be rebuilt during 1818. Less than forty years later the foundations of the second church were becoming unsafe and a third chapel was constructed, but by 1910 further renovations and repairs were necessary as it had become dilapidated. Lisvane Baptist church now meets in the Memorial Hall on Heol-y-Delyn Road. Methodist services are also held in the Memorial Hall.

Howell Harris, one of the most famous pioneer Calvinistic Methodist ministers, preached regularly during meetings held at several private houses in Lisvane between 1766 and 1769, just before his death.

Sports and recreation
Lisvane Cricket Club was formed in 1976. The club is now based at Llwynarthen in nearby St Mellons. They run 5 adult league sides, with the 1st XI playing in the South East Wales Cricket League Division 1, as well as running youth sides from Under 9 to Under 19.

Lisvane Panthers Junior Football Club fields sides in the under 8 Mini league, the Juniors at 11 – under16 and an over 16 youth team.

Lisvane Panthers Football Club, home ground Cardiff University pitches in Llanrumney, entered the Lazarou League in 2011. The team won three league and cup doubles (Division 4 in 2012, Division 3 in 2013, Division 2 in 2014) as well as reaching consecutive Lazarou Cup finals in 2013 and 2014.

Lisvane (CAC) Tennis Club is located just north of Lisvane and Thornhill railway station and is the tennis section of the Cardiff Athletic Club.

The nearest rugby union team is in nearby Llanishen.

Public services and village facilities
The area is served by Lisvane & Thornhill railway station with services northbound to Rhymney and southbound to Cardiff Central via Cardiff Queen Street.

Cardiff Bus operates services 27 (Thornhill/Birchgrove/Heath/Cathays), 28 (Llanishen/Roath),) and 86 (Llanishen/Heath/Gabalfa/Cathays) from Cardiff Central bus station through the area.

There are two pubs in Lisvane; the Ty Mawr and the Black Griffin, named after the Tredegar House Morgan family's arms that featured a gryphon, sable, segreant, and only recently returned to its traditional name having been called simply The Griffin for many years. There is a third pub called The Old Cottage just across the railway line that divides Thornhill and Lisvane.

A kilometre from the centre of the village is Parc Cefn Onn or Cefn Onn Country Park an extensive mixed species arboretum, with lakes and woodland walks. The park was laid out around ninety years ago and planted by the railway manager who lived in a large estate near Cefn Onn Halt, at the time Lisvane's tiny "request only" and underused railway station, which closed in 1985 when it was replaced by the current modern railway station closer to the village. Cefn Onn Halt stood a hundred metres away from the railway tunnel that vanishes under Llanishen Golf Club and Caerphilly mountain.

Notable people with Lisvane connections

 * Dave Edmunds, musician and record producer, lived in the village in the 1970s and early 1980s.
 * Alun Hoddinott, composer, lived in Lisvane until his death in 2008.
 * Sir Julian Hodge (1904–2004), founder of the Bank of Wales and the Jane Hodge Foundation. Hodge owned Ty Gwyn and later lived as a tax exile in Jersey.
 * Gwilym Jones, Member of Parliament and Under Secretary of State for Wales, 1992–1997, lives in Lisvane.
 * Robert Rogers, Baron Lisvane, Clerk of the House of Commons, 2011–14.
 * John Tabatabai, poker player, previously lived in Lisvane.
 * Joe Jacobson, footballer, grew up in Lisvane.
 * Rhys Griffiths, footballer, grew up in Lisvane.
 * Jimmy Floyd Hasselbaink, footballer, lived in Lisvane whilst playing for Cardiff City.
 * Luke Rowe, cyclist for SKY. Attended Llysfaen Primary School.

title: Lisvane


text:
Leptictidium

Leptictidium is an extinct genus of small mammals that were likely bipedal. Comprising eight species, they resembled today's bilbies, bandicoots, and elephant shrews, and occupied a similar niche. They are especially interesting for their combination of characteristics typical of primitive eutherians with highly specialized adaptations, such as powerful hind legs and a long tail which aided in locomotion. They were omnivorous, their diet a combination of insects, lizards, frogs, and small mammals. Leptictidium and other leptictids are not placentals, but are non-placental eutherians, although they are closely related to placental eutherians. They appeared in the Lower Eocene, a time of warm temperatures and high humidity, roughly fifty million years ago. Although they were widespread throughout Europe, they became extinct around thirty-five million years ago with no descendants, as they were adapted to live in forest ecosystems and were unable to adapt to the open plains of the Oligocene.

Description
Leptictidium is a special animal because of the way its anatomy combines quite primitive elements with elements which prove a high degree of specialization. It had small fore legs and large hind legs, especially at the distal side (that further from the body). The lateral phalanges of its forelegs (fingers I and V) were very short and weak, finger III was longer and fingers II and IV were roughly equal in size, and slightly shorter than finger III. The tips of the phalanges were elongated and tapered. The ankles and the sacroiliac joint were quite loosely fixed, while the pelvis had a flexible joint with only one coccygeal vertebra. The anteorbital muscle fenestrae in their crania suggest they probably had a long and mobile snout, similar to that of elephant shrews.

Leptictidium had wide diastemata in the antemolar row, its upper molar teeth were more transverse than those of the North American leptictids and its fourth premolars were molariform. Its C1 canines were incisiviform. Its dentition was quite small in comparison to the size of the mandible and the animal as a whole.

It varied between 60 and 90 cm in length (more than half of which belonged to the tail), and 20 cm in height. It weighed a couple of kilograms. These sizes could vary from one specimen to another. Leptictidium tobieni from Messel (Germany) is the largest known leptictid with skull 101 mm long, head with trunk 375 mm long, and tail 500 mm long.

Locomotion
One of the mysteries about Leptictidium is whether it moved by running or by jumping. Because there are very few completely bipedal mammals, it is difficult to find an appropriate living model to compare it with. If the kangaroo is used, it is probable that Leptictidium hopped along with its body tilted forward, using its tail as a counterweight. On the other hand, elephant shrews combine both types of locomotion; they usually move on four legs, but they can run on two legs to flee from a predator. Studies of the bone structure of Leptictidium have yielded contradicting information: its leg articulations appear too weak to have supported the shock of repeated jumps, but its long feet were obviously adapted for jumping rather than running.

Kenneth D. Rose compared the species L. nasutum with the leptictid Leptictis dakotensis. L. dakotensis had a series of traits which show it was a running animal which sometimes moved by jumping. Despite the marked similarities between Leptictis and Leptictidium, there are certain differences in their skeletons which prevent the example of Leptictis from being used to determine with certainty the way Leptictidium moved: the most important being that, unlike Leptictis, the tibia and the fibula of Leptictidium were not fused together.

Behaviour
Perfectly preserved fossils of three different species of Leptictidium have been found in the Messel pit in Germany. The marks on their fur have been preserved, as well as their stomach contents, which reveal Leptictidium were omnivores which fed on insects, lizards and small mammals. The holotype of L. tobieni also had pieces of leaves and notable amounts of sand in its abdomen, but it cannot be determined with certainty if the animal swallowed it.

Habitat
Leptictidium lived in the European subtropical forests of the Eocene. From the beginning of this period, the temperature of the planet rose in one of the quickest (in geological terms) and most extreme episodes of global warming in the geological record, termed Paleocene–Eocene Thermal Maximum. It was an episode of quick and intense (of up to 7 °C in high latitudes) warming which lasted less than 100,000 years. The thermal maximum caused a great extinction which is used to distinguish the Eocene fauna from that of the Paleocene.

The global climate of the Eocene was probably the most homogeneous of the Cenozoic; the temperature gradient from the equator to the poles was half that of today's, and the deep ocean currents were exceptionally warm. The polar regions were much warmer than today, possibly as warm as the present-day Pacific Northwest of North America. Temperate forests reached the poles themselves, while rainy tropical climates reached 45° N. The greatest difference was in temperate latitudes; nevertheless, the climate at the tropics was probably similar to today's.

In the Eocene, most of what is now Europe, the Mediterranean and south-west Asia was submerged under the Tethys Sea. These two continents were separated by the Turgai Strait (an epeiric sea). Due to high humidity and temperatures, most of the European continent was covered in vegetation.

The region which today is Germany was in a volcanically active zone during the Eocene. It is thought that the Messel pit could have been the old location of a volcanic lake saturated with CO2. The lake would periodically release the gas it contained, creating a lethal cloud which would asphyxiate any animal in its path. This would explain the great number of non-aquatic species which have been found in the old lake-bed of the Messel pit.

In the lush forests of this region, Leptictidium shared its habitat with animals such as Godinotia, Pholidocercus, Palaeotis, or Propalaeotherium. There were also predators, the crocodilian Asiatosuchus, the hyaenodont Lesmesodon, and the Messel giant ant.

Species
The genus Leptictidium includes eight species. These include:

Leptictidium auderiense
Described by Heinz Tobien in 1962 based on a series of lower jaws from the Lutetian faunal stage. Tobien also uncovered a small skeleton he defined as a paratype of the species, but Storch and Lister proved in 1985 that, in fact, the skeleton did not even belong to the genus Leptictidium. It was the smallest species of all and was only sixty centimetres long. Several skeletons have been found at the Messel pit. Mathis remarks the exceptional development of the paraconid (or mesiobucal cusp) of the lower P4 premolar. Its premolars and molars were quite small in comparison to the dentition as a whole. The name of the species refers to the Roman settlement of Auderia.

Leptictidium ginsburgi
Described by Christian Mathis in 1989. Fossils have been found in the lagerstätte at Robiac, Le Bretou, Lavergne, La Bouffie, Les Clapiès, Malpérié and Perrière (France), in Upper Ludian strata. The mesostyle typical of the genus Leptictidium is not developed in this species. The species is dedicated to Léonard Ginsburg, French paleontologist and deputy director of the Muséum national d'histoire naturelle in París.

Leptictidium nasutum
Described by Adrian Lister and Gerhard Storch in 1985. It was a middle-sized species which was seventy-five centimeters long. Several skeletons have been found in the Messel pit, in Lower Lutetian strata. The tail of this species had 42-43 vertebrae, a number surpassed among mammals solely by the long-tailed pangolin. Its premolar and molar teeth were quite small in comparison to the dentition as a whole. The name of the species refers to the nose of the animal. The holotype is the complete skeleton of an adult specimen kept in the Forschungsinstitut Senckenberg in Frankfurt am Main.

Leptictidium sigei
Described by Christian Mathis in 1989. Fossils have been found in the lagerstätte at Sainte-Néboule, Baby, Sindou and Pécarel (France), and it has a more primitive appearance than L. nasutum. It is known mainly from isolated teeth. It has a P4 with a much reduced paraconid, as well as very distinct entoconids and hypoconulids on M1 and M2. The species is dedicated to Bernard Sigé, French paleontologist.

Leptictidium tobieni
Described by Wighart von Koenigswald and Gerhard Storch in 1987. It was the largest species of all at ninety centimetres long. It is one of the species found in the Messel pit, in Lutetian strata. The species is dedicated to Heinz Tobien, descriptor of the genus Leptictidium and promoter of research in the Messel pit during the 1960s. The holotype is a complete and perfectly preserved skeleton of an adult specimen which was uncovered in September 1984 and which can be found at the Hessisches Landesmuseum Darmstadt. There is also a paratype; a non-complete and badly preserved specimen which can be found at the Institut Royal des Sciences Naturelles de Belgique.

It has a relatively robust mandible with a relatively large mesostyle. The molariform premolar teeth are a characteristic of the genus Leptictidium as a whole which is very marked in the P4 premolars of L. tobieni. The well-developed mesostyle and the transversal configuration of the upper molars are other typical traits of this species.

Comparison of the Messel species
By observing the clear morphological differences in the dentition of the three species found in Messel, the possibility can be discarded that either the discovered fossils are specimens of the same species but of different age, or that two of these forms belonged to the same species with a marked sexual dimorphism.

The Messel species developed very quickly a series of characteristic evolutionary traits, common to all of them, which separate them from the lagerstätte of Quercy.

This table compares the size of different specimens of each species found in the Messel pit (sizes in millimetres).

† From the front edge of the orbit. †† Above the incisura praeangularis.

Evolutionary tendencies
In his work Quelques insectivores primitifs nouveaux de l'Eocène supérieur du sud de la France (1989), French paleontologist Christian Mathis studied the evolutionary tendencies of the genus Leptictidium, based on comparison of the most primitive and the most recent species. From his observations, Mathis remarks:

 * an increase in size;
 * a precocious merging of the hypoconulid and the entoconid on M3;
 * a slight reduction of the width of the talonid on M3 in comparison to the anterior molars;
 * the formation and development of a mesostile on the molariform jugal teeth P4-M3;
 * the reduction of the parametastylar and metastylar regions of these same teeth (with some exceptions), in particular with a reduction of the parastylar lobe which rises less in the anterior part of M3 and possibly P4;
 * a transverse shortening of the upper molarised teeth, which become more square;
 * the development of accessory conuli on the preprotocrista and postprotocrista;
 * the development of the postcingulum.

title: Leptictidium


text:
Radyr

Radyr (Radur; ) is an outer suburb of Cardiff, about 4 mi northwest of Cardiff city centre. Radyr is part of Radyr and Morganstown Community, for which the 2011 Census recorded a population of 6,417.

Morganstown is north of Radyr, on the other side of the M4 Motorway. Neighbouring communities are Whitchurch to the east on the opposite bank of the River Taff, Pentyrch to the west with St Fagans and Llandaff to the south.

Stone Age until the Norman Conquest
Evidence of Stone Age occupation of the Lesser Garth Cave near Morganstown was discovered in 1912 and included worked flints. In 1916 excavation of a mound of 30 m in Radyr Woods revealed charcoal and Iron Age pottery. Radyr developed after the Norman invasion of Wales at the start of the 12th century and formed part of the Welsh Lordship or cantref of Miskin under the Lordship of Glamorgan created by the Norman King, William Rufus, in 1093.

Origin of the name
Hints about the derivation of the name Radyr can be found in Lifris's writings Life of St Cadog, written between 1081 and 1104 but relating to the earlier period around AD 530, which mentions a croft or tref on the site called Aradur Hen. Lifris also tells the story of Tylyway, a hermit who was held to have lived on the banks of the Taff. Tylyway's cell is the most likely origin of the name Radyr; from the Welsh yr adur, meaning "the chantry", although Arudur Hen is also possible.

Norman occupation and Middle Ages
The Norman motte in the "mound field" is a flat-topped mound 30 m in diameter at the base and 3.8 m high, surrounded by a ditch 7 m wide. An adjoining bailey to east of the motte could indicate the boundary between Norman and Welsh land. The motte was surrounded by a timber palisade around a wooden keep and formed part of a defensive line with similar mottes at Thornhill and Whitchurch. The early settlement that became Radyr developed around the Norman church and manor house in what is now Danescourt. Surveys in 1307 describe an agricultural hamlet surrounded by arable fields. The 14th century Welsh Lord of Radyr, Cynwrig ap Hywel, followed by his descendants, farmed the area until it was devastated by the Black Death and by battles between the Marcher Lords in 14th and 15th centuries when the whole area was laid waste.

Mathew family
In 1469 Thomas Mathew (died 1469), the third or fourth son of Sir David Mathew (died 1484) of Llandaf, inherited the land by marriage to Catherine, heiress of Radyr, and built Radyr Court, a manor house on the site of what is now the Radyr Court Inn in Danescourt. The house was used as a court. Although it was destroyed by a fire in the 19th century, the three large dungeons survived and can still be seen at the Inn. On Thomas' death, his lands passed to his eldest son David and then to his younger son William Mathew (died 1528), who was knighted by King Henry VII at the Battle of Bosworth in 1485. Sir William accompanied Henry VIII to the Field of the Cloth of Gold in 1520. His successor was his eldest son Sir George Mathew, who became MP for Glamorganshire and in 1545 Sheriff of Glamorgan.

Sir George created a deer park that ranged far north of Radyr. Tenant farmers there were evicted, and the loss of rental income contributed to the decline in the family's fortunes. He had 24 children, eight of whom were illegitimate. Many were daughters, and Sir George needed large sums of money for their dowries. On his death Sir George's lands passed to his eldest son William, who also became an MP and invested in the Pentyrch ironworks. This was an astute move as feudalism was giving way to early industrialisation. William's descendants inherited a diminishing fortune. Captain George Mathew, the last of the family to live in Radyr, married Elizabeth Poyntz, and the couple left Radyr to live on her estates at Thurles in County Tipperary, Ireland in 1625.

Stuart period
Radyr's new owner was a wealthy landowner, Sir Edward Lewis, who was knighted by James I. Sir Edward owned St Fagans Castle and its surrounding lands, scene of the Battle of St Fagans in the English Civil War. The Lewis fortune passed to Elizabeth Lewis, who married Other Windsor [sic], 3rd Earl of Plymouth, the principal landowner in Cardiff, Penarth and Barry.

A survey in 1766 shows that the Plymouth family owned the freeholds of most of Radyr. It continues to do so today. Plymouth Estates sold 22 acre of residential land in Radyr in 2007.

Development from the 18th century
Many residents of Radyr worked in the Melingriffith Tin Plate Works, on the other side of the River Taff in Whitchurch. The works opened in 1749 and closed in 1957.

Samuel Lewis' 1849 Topographical Dictionary of Wales says of Radyr:

"'A parish, in the poorlaw union of Cardiff, hundred of Kibbor, county of Glamorgan, in South Wales, 3½ miles (N. W. by W.) from Cardiff; containing 279 inhabitants. This parish probably derives its name, signifying 'a cataract,' from the rushing waters of the river Tâf, by which it is bounded on the north-east. It was formerly comprehended within the hundred of Miskin, but has been recently separated therefrom. It comprises about eleven hundred acres of arable and pasture land, inclosed and in a profitable state of cultivation: the surface is in some parts elevated, and in others flat, but no where subject to inundation; the soil is a strong brown earth, favourable to the production of good crops of grain of all kinds, potatoes, and hay. The substratum is partly a hard brown stone, and partly limestone of very good quality. Radyr Court, formerly the seat of the family of Matthew, ancestors of the late Lord Llandaf, has been partially taken down, and the remainder has been modernised, and converted into a farmhouse. The turnpike-road leading from Cardiff to Llantrissent passes a little to the south of the parish; and the Tâf-Vale railway runs through it, nearly parallel with the river, which is crossed by the line in this vicinity. Some of the inhabitants are employed at the iron-works in the parish of Pentyrch."

"The living is a vicarage, endowed with £200 royal bounty; patron and impropriator, the representative of the late Earl of Plymouth, who is lord of the manor: the tithes have been commuted for £113. 9s. 0d, of which a sum of £38. 9s. 0d is payable to the impropriator, and a sum of £75 to the vicar. The church, dedicated to St. John the Baptist, is a neat plain edifice, with a curious turret at the west end. There is a place of worship for Calvinistic Methodists; a Sunday school for gratuitous instruction is held in it, and another at Radyr Court. In the parish is a spring of very cold water, called Y Pistyll Goleu, 'the bright water-spout,' issuing from the side of a hill, under a considerable depth of earth over a limestone rock: it has by some writers been termed mineral, but it is not known to possess any other properties than that of its extreme coldness, which renders it efficacious in curing sprains and weakness of the sinews.'"

Until the mid 19th century Radyr was a collection of small farms, crofts and cottages, but after Radyr railway station opened in 1863, the population rose from 400 to more than 600 in 20 years. The Taff Vale Railway and its successor, the Great Western Railway, brought significant employment to Radyr. Junction Terrace (the first street in Radyr) was built to house the railway workers. It was the start of strong demand for housing in Radyr that transformed the hamlet. The Barry Railway's Walnut Tree Viaduct, built in 1901, dominated the village for some 70 years.

Wartime
In the First World War the community raised funds for a "Radyr bed" at the nearby Welsh Metropolitan Military Hospital in Whitchurch and established a "Citizen Guard" made up of those too old or too young to enlist. Losses suffered by the village are recorded on the War Memorial in Heol Isaf.

In the Second World War thousands of children were evacuated from metropolitan areas such as London, Birmingham and Liverpool. One evacuee from Woolwich, Patricia Armstrong aged nine, was knocked down by a passenger train and killed on a Saturday afternoon in May 1943 while using the Gelynis foot crossing at Morganstown. She was lodged with a family in Morganstown. As air raids on Cardiff increased, even younger children from Radyr were evacuated to boarding schools at Rhoose and Bridgend.

Post-war history
An extensive housebuilding programme started in the 1960s, and Radyr's population grew rapidly — particularly children. In 1964 Radyr Comprehensive School had 135 pupils on its roll. This number more than trebled in the next decade. A new development, the Danescourt estate, was built on land surrounding Radyr Court and St John the Baptist parish church, and the land was officially incorporated as a suburb of Cardiff in 1974. Danybryn Woods, near the development, was retained as the entire forest is protected by a tree preservation order and is home to many species of plants and wildlife. Radyr railway station was renovated in 1998 and the tracks through the station were renewed, reducing journey times to Cardiff city centre.

In 2017 construction started on the first phase of a new Cardiff suburb of 7,000 houses, named Plasdwr, on countryside along the Llantrisant Road between Radyr and St Fagans.

UK Parliament and Senedd
Radyr is in the Cardiff West parliamentary constituency and the Cardiff West Senedd constituency.

Cardiff Council
Radyr electoral ward (often known as Radyr and Morganstown) has one seat on Cardiff Council and had an electorate of 4,368 (1 May 2008). The ward elected a Conservative, Roderick McKerlich, in the election of May 2008 and he was re-elected in 2012 and 2017. Cllr McKerlich is a member of the Council's Environmental Scrutiny Committee.

Community Council
Radyr and Morganstown Community Council is funded by an addition to the Council Tax bill paid by local residents. The Community Council is run by 11 elected councillors from three wards in the parish – Radyr North (4 seats), Radyr South (3 seats) and Morganstown (4 seats) - subsequently increased to 12 councillors (4:4:4).

Geological structure
The surrounding soils are mostly a strong, brown, dry earth, well adapted for arable farming and the growing of grains of all kinds that contributed to the area being a mostly farming community until the modern era. Soils were further enriched over the millennia by alluvial deposits from the River Taff. The bedrock under the whole area is predominantly sandstone, dating from both the Devonian period (Old Red Sandstone) and the Triassic (New Red Sandstone) laid down in arid conditions. These may subsequently have been ground down by the Taff valley glacier during the last ice age around 18,000 years ago. Radyr Stone is a Triassic breccia used widely for decorative work in the Cardiff area, including Llandaff Cathedral, Cardiff Docks and in the bridges of the Taff Vale Railway.

Radyr Weir
The River Taff at this point runs roughly south through Taff's Well, past Radyr and through Llandaff.

Radyr Weir was built in 1774 to divert water into a leat to the Melingriffith Tin Plate Works. The weir is the third obstacle to migratory salmon and sea trout — the others being Llandaff Weir and Blackweir, both of which also have fish passes. Since the early 1980s, the salmon and sea trout stocks in the Taff have been recovering from nearly 200 years of industrial pollution and exploitation. In 1993 the National Rivers Authority monitored over 500 salmon and 700 sea trout returning to the river to spawn.

From 1749, iron from Pentyrch was initially transported to the works using pack-horses, then tub boats were used on the Taff passing onto the feeder via a lock at Radyr Weir. Parts of this lock can still be seen beside the feeder sluice. In 1815 the tub boats were discontinued and a tramway built along the Taff. There is a public picnic site by the Radyr weir.

A hydro-electric scheme was built in 2016 on Radyr Weir to generate renewable energy. The Radyr Weir scheme channels more than 500 million cubic metres of water per year through two screw turbines and is expected to generate 400 kW — enough energy to power three of the city’s leisure centres — which will save 700 tonnes of CO2 annually.

The River Taff through Radyr is flanked on both sides by an undeveloped greenway that passes uninterrupted through northern Cardiff all the way to Cardiff Castle in the centre of the city, before the river enters Cardiff Bay.

Radyr Woods Nature Area
Radyr Woods is a Site of Importance for Nature Conservation (SINC), under the name Radyr Community Woodlands, covering 15.6 acre, and the adjoining Hermit Woods is the smallest Local Nature Reserve (LNR) in Wales, at 1.47 acre). The Community Woodlands have a network of footpaths and boardwalks and includes evidence of Iron Age settlements and remains of an early cooking hearth. Originally part of the Tudor deer park owned by the Mathew family and later Radyr Quarry, the area is owned by Cardiff Council and Plymouth Estates, and managed by the Radyr community council with the support of Cardiff Council's Parks Service.

Radyr Woods provides habitats for a wide range of species. It also has a number of natural springs that feed a duck pond and a kingfisher pond. Recent housing developments between the reserve and the railway line have added complementary public open space with picnic areas and a children's play area. Since 1986 all maintenance and development of the reserve has been carried out by a volunteer group known as The Friends of Radyr Woods.

Radyr hawkweed
Radyr hawkweed is the common name of Hieracium radyrense, a very rare endemic member of the aster, daisy, or sunflower family. It is a microspecies, so far only identified at Radyr. It was first identified in 1907 at the quarry, was described as a variety in 1948 and then as a separate species in 1955. It has rarely been seen and regular surveys between 1998 and 2004 indicate that today only a single population of about 25 plants survives in the wild. In the first survey of 1998, only nine plants were identified in one single Radyr garden, where it traditionally grew on grassy banks and lawns, often in shade. It was no longer found at the original locality of Radyr Quarry where examples were last seen in 1985. At Bridgend, six possible plants of the Radyr genus were found on an old garden wall, but confirmation of identification is still awaited.

Neither the species nor the sites have any current legal protection, and it could be under significant threat of survival in the long term from inappropriate gardening or care. Seed samples of the Radyr hawkweed have been provided to the Millennium Seed Bank, the international conservation project coordinated by the Royal Botanic Gardens, Kew, and plants are being carefully cultivated. The plant normally flowers between May and early July and Radyr residents are urged by botanists to be on the look out for further examples of the endangered species while walking in the area.

Demography
The 2001 census showed that the suburb had a total population of 4,658, of whom 2,268 were male and 2,390 were female. The average age was 39.7 years. 68.27% of [adult] residents are married, with 20.81% having never married. 73.97% declared their religion as Christianity. 23.97% stated no religion and 0.9% stated Muslim. 96.02% stated their ethnicity as white, 1.76% as Asian, 1.03% as mixed race, 1.01% as Chinese, and 0.2% as Black. 15.5% are Welsh language speakers.

Landmark buildings and local attractions
Danybryn Cheshire Home was once a private house owned by Sir Lewis Lougher MP. It later had two wings added to accommodate the residents, who are physically disabled young people. The Thatch, the only thatched cottage in Radyr, was built for the Mathias family in 1936. St John the Baptist parish church is nearly 800 years old, but underwent a Victorian restoration in the 19th century.

The Taff Trail cycle path passes through Radyr via Radyr Weir. Other notable buildings include The Old Church Rooms and Radyr War Memorial. In nearby districts are St Fagans National History Museum (formerly the Museum of Welsh Life) and Castell Coch.

Education
The Church Rooms in Park Road were also a primary school until 1896 when the Board School was opened next door. Older pupils had to travel to secondary schools in Penarth by train. The part-time Radyr Library serves the area.

Nursery and primary schools
Bryn Deri Primary School was opened in 1976 and has included a nursery school since September 1999. Radyr has also a private pre-school, Park Road Nursery, and a Welsh-language nursery called Cylch Meithrin, both of which are based in the Old Church Rooms.

Radyr Primary School in Park Road opened in 1896, and new classrooms were added in 1968 to accommodate the rising population. The school currently has 11 classes and over 300 pupils.

Secondary education
Radyr Comprehensive School has more than 1,400 pupils from across west Cardiff. It also has a large Sixth Form college with about 300 students, and an active adult education centre. In March 2021, Radyr Comprehensive School was the scene of a major incident where "malicious communication" was phoned through to the school. Armed police attended the scene and all pupils were successfully evacuated from the school.

Churches
The Church in Wales Parish of Radyr is in the Diocese of Llandaff. The parish church of St John the Baptist, beside Radyr Chain, is now surrounded by the Danescourt housing estate. It is nearly 800 years old but was altered in the 19th century. It is a Grade II listed building.

Christ Church, although a larger building than St John's, is the daughter church in Radyr. Designed by the Llandaff diocesan surveyor George Halliday, the nave was ready for use at Easter 1904 and the chancel and tower were completed in November 1910. Also in 1910 John Taylor & Co of Loughborough cast a ring of eight bells for the tower. Lieutenant Colonel Fisher paid for the bells, and each bell is inscribed with the names of members of his family.

Radyr Methodist Church in Windsor Road replaced an earlier Methodist Church in Heol Isaf. Radyr is also served by Radyr Baptist Church, which worships in the Old Church Rooms in Park Road.

Sport and leisure

Llandaff North RFC is the closest rugby team to Radyr. Nearby Taffs Well RFC was formed in 1887, and has provided three former Welsh Rugby captains and six Welsh International players during its history.

Radyr Golf Club was founded in 1902 after moving from its original nine-hole course at the Tŷ Mawr in Lisvane. It is a 6109 yd, par 70 (SSS 70) course for men and 5510 yd, par 73 (SSS 73) for women, and operates all year round. Laid out by the course designer Harry Colt, the Chairman of the 2010 Ryder Cup recently described Radyr's course as "One of Colt's Little Jewels".

Radyr Lawn Tennis Club was founded in 1914 by 20 Radyr 'Gentlemen', helped by the Earl of Plymouth Estates. Its first location was near the railway station but the courts were badly laid. Again with the help of Plymouth Estates, the club lifted the turf from all three grass courts and relaid it on its current site next to Christ Church on Heol Isaf.

Radyr Cricket Club was founded in 1890 by the Earl of Plymouth, who granted a hundred-year lease for the current riverside ground to the local residents for a nominal sum. The pavilion was destroyed by fire in 1973 while the team were away on tour. Under the leadership of the new Chairman Keith Terry, a huge fund-raising effort was made and a new pavilion opened on the footprint of the old one in 1975. Radyr currently plays in the first division of the South Wales Premier Cricket League.

Cardiff Corinthians Football Club (known locally as the "Corries") has played its home games at the Riverside Football Ground in Radyr since 1974 and competes in the first division of the Welsh Football League.

The main shops in Radyr are in Station Road. One of the buildings on this road, Bryn Melyn, is now a dental surgery but was formerly the village post office.

Rail
At the turn of the 20th century Radyr had a busy railway from where coal trains were transferred onto either the Taff Vale Railway to Cardiff Docks, or the Penarth district line to the docks at Penarth, 4 mi southwest of Cardiff city centre. Also, the Barry Railway Company freight route ran just to the north of Morganstown, over Walnut Tree Viaduct. To the south-east of Radyr was an extensive railway marshalling yard which included another railway bridge over the Taff to provide an alternative route towards Llandaff. The sidings were lifted in preparation for a housing development in the 1970s.

Radyr railway station still handles significant traffic, with over 200 trains calling each weekday and more than 400,000 passenger journeys per year. Radyr is the northern terminus of the Cardiff City Line.

Bus
Cardiff Bus route 63 and Stagecoach South Wales route 122 operate from Morganstown and Radyr to Cardiff Central bus station via Danescourt, Llandaf and Pontcanna.

Road
The B4262 road (Heol Isaf) runs through the centre of Radyr and Morganstown, leading north to Taff's Well and the A470 towards Pontypridd, and south to the A4119 (Llantrisant Road), which links Llantrisant with Danescourt, Llandaff and Cardiff city centre.

The M4 corridor around Cardiff was announced in 1971 as a replacement for a northern link road that had been planned since 1947 but never built. The northern "Lisvane and Radyr route" for the M4 was eventually chosen after a number of noisy public enquiries and active objections by residents from both communities. The new motorway was completed and opened on 10 July 1980, and passes east–west between Radyr and Morganstown. Later this section was widened to three lanes in each direction at a cost of over £71 million, being completed in December 2009. Radyr has no direct access to or from the motorway.

Notable people
Several notable people are associated with Radyr. The children's author Roald Dahl (1916–90) lived in the 1920s at a house called Tŷ Mynydd in Radyr (which was demolished in 1967). He called it an "imposing country mansion, surrounded by acres of farm and woodland" in his book Boy: Tales of Childhood. Jimi Mistry (born 1973), who is an Asian-British actor and appeared in EastEnders, The Guru and East Is East, attended Radyr Comprehensive School. Actor Harry Ferrier also went to Radyr Comprehensive as he grew up in Radyr. and Tess Griffiths (Nee Davies).

Local sportsmen include Harry Corner (1874–1938), an English cricketer who played in the Great Britain team that won a gold medal at the 1900 Summer Olympics, who lived, died and was buried in Radyr. Hugh Johns (1922–2007), who was best known as a football commentator for ITV, retired and died in Radyr. Frank Meggitt (1901–45), a Welsh cricketer, a right-handed batsman and wicket-keeper who played for Glamorgan, also lived in the town after retiring from the sport. The athlete and runner Timothy Benjamin (born 1982) was born and raised in Radyr.

Another notable resident is Sir Martin Evans (born 1941), the Professor of mammalian genetics at Cardiff University who received the Albert Lasker Award for Basic Medical Research in 2001, was knighted in 2003 and was awarded the 2007 Nobel Prize for medicine for his work on stem cells. He is also a Fellow of the Royal Society and a Fellow of the Academy of Medical Sciences.

Radyr in the media
The outdoor scenes in an episode of the TV science fiction series Torchwood, called Small Worlds, were filmed mostly around Radyr Primary School.

title: Radyr


text:
Bruchterveld

Bruchterveld is a village near the town of Hardenberg, Overijssel, the Netherlands. There is a village house and a football association. It has three churches: Dutch reformed, Dutch reformed freed and Reformed.

History
It was first mentioned in 1868 Bruchter Veld, and means "field belonging to Brucht". It was a heath and peat area which was excavated during the 19th and early 20th century.

title: Bruchterveld


text:
Heath, Cardiff

Heath (Y Mynydd Bychan) is a district, community and coterminous electoral ward in the north of Cardiff, capital of Wales. It is a predominantly affluent area with property prices being the third highest in the city. The area is known for its traditional 1930s detached and semi-detached properties with large south facing gardens. Roads are tree lined and large greeneries with the notable attraction of Heath Park and the joining of the University Hospital of Wales.

The population of the ward and community taken at the 2011 census was 12,629.

Description
Heath was originally called the Great Heath and named as a result of the large park and woodland that it once contained. After the initial development of traditionally middle-classed semi-detached housing (1920s-1950s) and more recently the construction of the University Hospital of Wales on the site of the former Heath Wood (1960s), much of the greenery has been eradicated. It should be distinguished from the Little Heath (Y Waun Ddyfal) which lies to the south of the Great Heath, in the vicinity of Crwys Road.

The 91 acre, (37 hectare) Heath Park forms the remainder of this area of grass and woodland. It includes attractions and facilities such as the George V Playing Fields, tennis courts, a miniature steam railway and refreshment facilities.

Birchgrove is a busy shopping area that is part of the ward of Heath. It is composed mostly of more affordably priced housing, mainly terraced, and has taken on an identity of its own.

The area around the University Hospital of Wales has been known as Saints Corner, due to the number of streets in the area named after well known saints.

The Welsh language
The number of Heath residents over three years old who speak Welsh increased from 1,378 in the 2001 UK Census to 1,422 in the 2011 UK Census. In percentage terms there was a slight decrease (from 12.1% to 11.7%). This was caused by a reduction in the number of speakers over the age of 65; the age groups 3–15 and 16—64 both showed increases.

Rail
The area is served by two railway stations. Heath Low Level is on the Coryton Line, linking Central and Coryton stations. Heath High Level is on the Rhymney Line, linking Central and Rhymney stations via Llanishen, Lisvane Thornhill and Caerphilly.

Bus
Cardiff Bus's routes 38 and 39 terminate at the University Hospital of Wales, originating from the City Centre. The 8 now operates between the City Centre and Grangetown, while the 9/9A operates from the City Centre to IKEA and Cardiff Bay, including the Sports Village. The 86 service runs to Lisvane via Heath. The following services run through west of Heath:
 * 1/2 (City Circle)
 * 21 (Central Stn)
 * 23 (Whitchurch/Rhiwbina)
 * 24 (Whitchurch/Llandaff/Canton)
 * 25 (Central Stn)
 * 27 Capital City Green (Thornhill/Birchgrove)
 * 35 (Gabalfa or Cardiff Bay)

Walking and cycling
Cardiff Council have recently implemented a number of traffic calming measures on Allensbank Road / Heath Park Avenue with the aim of slowing traffic on the major thoroughfare and improving safety for pedestrians. The council also has plans for Cycleway 1 to run through the area, continuing on from Gabalfa to the neighbouring ward of Cyncoed.

Governance
Westminster: As part of Cardiff North, Heath has been represented at Westminster since 2017 by Anna McMorrin MP (Welsh Labour)

Senedd Cymru – Welsh Parliament: As part of Cardiff North, Heath has been represented in the Senedd since 2011 by Julie Morgan, MS (Labour)

Heath is both an electoral ward, and a community of the City of Cardiff. There is no community council for the area.

The electoral ward of Heath falls within the parliamentary constituency of Cardiff North. It is bounded by Rhiwbina and Llanishen to the north; Cyncoed to the east; Gabalfa and Cathays to the south; Llandaff North to the southwest; and Whitchurch & Tongwynlais to the west.

Cardiff Council: Since May 2017 Heath is represented on Cardiff Council by three councillors, Lyn Hudson (Conservative), Graham Hinchey (Welsh Labour) and Fenella Bowden (Heath & Birchgrove Independents). Cllr Bowden had been a member of the Liberal Democrats but left, to sit as an Independent councillor, in November 2010. In the past it has been represented by a variety of political groups, moving from Labour in the 1990s, to all Liberal Democrat in May 2004 and, after the May 2008 election, a Conservative majority.

title: Heath, Cardiff