Talk:Quasicrystal

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A couple of other sources ([[1]], [[2]]) state that Schechtman observed quasicrystals in 1984, but this article says 1982. Which is correct?

Crust 15:04, 1 Feb 2005 (UTC)

Shechtman et al. discovered the quasicrystalline phase in 1982 and published their results in 1984 (Phys. Rev. Lett. 53 (1984) 1951). —Preceding unsigned comment added by 140.105.8.31 (talk • contribs)

Contents

[edit] Potential Uses of quasicrystals

I am currently reading a book on Atlantis which explains the use of quasicrystals as "libraries", storing massive amounts of information which is programmed into them telepathically. Does anyone have some information on this or telepathy in any state? Skeptics need not respond —Preceding unsigned comment added by Nonskeptic (talk • contribs)


No need to answer to the last comment, but quasicrystals have been used indeed for practical applications. Due to their low friction coefficient they have been used as coating in frying pans by a french firm. quasicrystals are also promissing materials for hydrogen storage especially the Zr-Ti-Ni alloy. —Preceding unsigned comment added by 69.138.202.161 (talk • contribs)

[edit] "bent" linear subspaces?

In a quasicrystal, flaws are locations where the 3D "subspace" is bent, or wrinkled, or broken as it passes through the higher-dimensional space.

seems to contradict the earlier description of non-periodic tilings (in that definition, the subspace was linear!). Can anyone clarify?

RandomP 01:24, 28 April 2006 (UTC)


[edit] Needs Revision?

I think that this article should be thoroughly revised. Since Shechtman's discovery many new experimental results have been reported. In physics 'Quasicrystals' has been a fashionable topic during the last 20 years, with lots of popular examples. Mathematicians have also taken some interest in this recent development. And now there is a pile of books with 'quasicrystal' in the title. None of this is apparent in the article. (I have added a few lines, but an expert is needed to rewrite all.)15:32, 28 June 2006 (UTC)After some reading, did some more rewriting but it is still far from being acceptable .al 14:34, 28 January 2007 (UTC)

Removed:

It is a nice picture but not exactly a quasicrystal; relevant material can be seen at the external links.al 17:51, 18 September 2006 (UTC)

[edit] 1D quasicrystals?

Are one dimensional quasicrystals possible? Can anyone give me an example(mathematical example is fine) of a 1D quasicrystal?


(Check the link to S.Weber's Introduction):

10110101101101011010110110101101101011010110... The Fibonacci sequence is a standard example of 1D quasicrystal: it is neither ordered ('crystal') nor disordered ('noise'). The Fourier transform of such nonperiodic systems with well defined long range order exhibits delta peaks with spacings which are fractions of some irrational number. The absence of this feature is taken as a sign of insufficient long range order and then the systems are taken to be closer to random ones. The Bombieri-Taylor argument allows eventually to identify the quasicrystals.195.96.229.95 07:44, 7 August 2006 (UTC)


[edit] Examples of quasicrystals

Maybe we can link to examples of quasicrystals that have their own page in wikipedia? One family of quasicrystals is the high temperature superconductors Bi-2201, Bi-2212, Bi-2223. They have a crystal unit cell that's modulated by a displacment function whose wavevector has irrational components. --spiralhighway 07:41, 14 August 2006 (UTC)

PS: By the way there's a great review article about all this stuff by Akiji Yamamoto: Acta Cryst. A52, 509-560 (1996)

I added a link to a NPR.org story about medieval architectural tiling in the middle east. I know this is a link to an artistic use of a math concept, but then that's an interest of mine, and I hadn't heard of quasicrystals before. Listening to the story, I kept expecting them to mention fractals. [MDR 22 February 2007]

[edit] Needs improvement

The grammar and spelling need improvement in the main article.

—The preceding unsigned comment was added by 81.153.174.184 (talk) 10:22, 6 February 2007 (UTC).

[edit] This article is not very informative

This article contains a lot of information about the discovery and publication in this field, but does not do a good job in describing quasicrystals. —The preceding unsigned comment was added by 70.153.26.74 (talk) 22:30, 22 February 2007 (UTC).

[edit] Quasicrystalline designs in medieval Islamic architecture?

The article at: http://news.yahoo.com/s/nm/20070222/sc_nm/architecture_patterns_dc_1 suggests there is basis for concluding that Medieval Muslims had some knowledge of quasicrystalline patterns over 500 years ago. Should the main encyclopedia article on Quasicrystals make some reference to these theories? —The preceding unsigned comment was added by Brad Bridgewater (talk • contribs) 05:31, 23 February 2007 (UTC).

Interesting. I was just reading the same thing on Reuters. Yes, I believe it merits a line or two in the article. http://www.reuters.com/article/scienceNews/idUSN2245118920070222?src=022207_1643_ARTICLE_PROMO_also_on_reuters&pageNumber=1 82.167.21.196 13:22, 23 February 2007 (UTC)

I added a short reference to the Lu and Steinhardt article in Science at the end of the "Brief History" section. That doesn't flow with the chronology (since it refers to a possible usage of quasi-crystalline patterns over 500 years before their "discovery" by Penrose et al.) but seemed less disruptive of the main discussion.Bridgewater 23:07, 23 February 2007 (UTC)

It is a pitty that no mention of this interesting finding is made in the body of the article. The readers deserve to know the fact that the quasicrystal-style tilings were used in decorations in the Middle East about 500 years ago. Some people would like to play down this fact by saying that most likely they were not aware of the implications of such a thing. My question is what better implication does one need other than actually trying to use it to tessellate a plane successfully in a real world application? 71.103.51.35 (talk) 23:32, 9 February 2008 (UTC)Ur

Quasicrystals are a natural (i.e. physical) phenomenon. In natural history physical phenomena precede biological and cultural ones, so quasicrystals precede artisanal artefacts. Removed two passages which begin by stating:

  • "The earliest quasicrystal patterns date back to the girih tiles found in medieval Islamic architecture...
  • "Recently discoveries have shown that quasicrystal patterns were first employed in the girih tiles found in medieval Islamic architecture..

They are obviously incorrect or at least badly worded and also they are out of context. Please read the old comments in the section below and provide some answers before reverting once again. Item 6 is rephrased here: the article pertains to physics where tilings, mathematical or artisanal, are just models.al (talk) 18:58, 4 March 2008 (UTC)

[edit] Reverted

I believe that all of this is a misunderstanding and have reverted to a previous version. Here is why:

0.In these recent writings 'quasicrystalline' is used as a synonym for aperiodic.

1.'Quasicrystalline' means aperiodic and diffracting. Islamic decorators were interested in elegant and complicated designs but there is no ground to think they knew or cared about aperiodicity and diffraction. And even less that they understood quasicrystals which require both.

2. Aperiodic is not necessarily complicated in an obvious way: a square grid of lines with spacing following the binary fibonacci sequence is aperiodic (and diffracting). Any finite structure may be repeated so the term 'aperiodic' implies infinity and needs a conceptual proof. Obviously these points are outside artisanal interest. Drawing a straight segment is not the same as having the concept of a line.

3. Unusual or exotic symmetry is not mandatory for a qc. But without it the diffractive picture would not reveal aperiodicity and some other method is needed. The diffractive property is of interest as it implies indefinitely extended long-range order.

4. In the Reuter's hype the first reference to qc ('quasicrystalline') is rightly in quotes. And for a finish they quote Socolar, an undisputed authority, who attempts to avoid some misnomers and misunderstandings.

5. Speaking of discoveries is tricky if one does not want to credit plants with the discovering of the Fibonacci sequence; obviously the AlMn alloy did not discover the quasicrystals. There is a difference between mathematics and other natural phenomena or simple practices.

6 The link from decorations to quasicrystals goes through [[aperiodic tiling]] and a 'shortcut' here is out of place. The new additions were inaccurate and incorrect.

My hope is that readers and contributors to Wikipedia should be able to distinguish facts from hype.al 13:17, 3 March 2007 (UTC)

Steinhardt and Lu published some 'Further notes on quasi-crystal tilings' in Science, Vol. 316. no. 5827, pp. 981 - 982 (May 18, 2007) downplaying their previous claims. There are no hints that the possibility of aperiodicity has been considered, so they state: "Our conclusions were guarded, concurring with the remarks by Socolar and Levine in the accompanying news article, suggesting that evidence beyond a single large fragment is needed to prove that the designers understood this possibility. "al (talk) 19:51, 4 March 2008 (UTC)

[edit] Reversion Was Excessive

The reference to P. J. Lu and P. J. Steinhardt, Decagonal and Quasi-Crystalline Tilings in Medieval Islamic Architecture, Science Vol. 315 no. 5815, 1106-1110 (2007) that you deleted, al, was not hype. You seem to have a disagreement with Lu and Steinhardt, but that is no reason for deleting a reference to their work. I note that P.J. Steinhardt is the very same Steinhardt that the article still cites as an author of the first paper to use the term "quasicrystal." I would concur, however, in the deletion of the more florid text from the popular press.Bridgewater 23:00, 7 March 2007 (UTC)

Please explain what these decorations have to do, not with aperiodic tilings, but with quasicrystals per se. Quoting the name of Steinhardt does not answer any of the objection made above.
Any adman would agree that 'aperiodic' obviously bears negative connotations while 'quasicrystalline' sounds decidedly more positive. And his advice probably would be to use the second even if it is inaccurate. Called this 'hype' for short.
My disagreement is not with Steinhardt and Lu but with the mention of their work here.al 22:28, 16 March 2007 (UTC)
Completely concur. —Preceding unsigned comment added by 69.152.220.72 (talk) 14:28, 28 September 2007 (UTC)

[edit] The french WP page -

about quasi cristal looks like it were more complete, giving history, references and all. IANACrystallographist myself, but it may be interesting to take a look. Thanks. -- DLL .. T 20:00, 8 April 2007 (UTC)

[edit] Illustration

Illustrating articles with works of art, related by name only, does not seem to be an acceptable option here: it would be ok in a magazine, but not in an encyclopedia. Removed 'a quasicrystal artwork', Painting 2006-7( Image:Tony Robbin artwork.JPG) by Tony Robbin. I will be looking for something literal.al 22:07, 14 August 2007 (UTC)

[edit] Aperiodic tilings are not the same as quasicrystals

The article is starting to shape up, but there could be more clarification of the distinction between the physical materials -- quasicrystals-- and the mathematical topic of aperiodic tiling.

In particular, the discussion of Wang's & Berger's, and to a much lesser extent Penrose's contributions to the study of Aperiodic Tilings, seems over-emphasized here. To this day no one knows why or how quasicrystalline materials form. One thing is absolutely known: defect-free, reliably non-periodic tilings cannot be assembled from local rules. In other words, quasicrystals are not perfect aperiodic tilings created by atoms coming together one by one by local interactions. Any one of these clauses might possibly be deleted, though, for a working model.

The point is, the structures formed by aperiodic sets of tiles and the structure of quasicrystals have some of the same gross features-- but that might be about it.

As far as Lu and Steinhardt's paper, again, it is not really clear that that deserves much attention in this article. They were not claiming-- quite obviously not!-- that islamic architects were interested in unusual Al-Mn alloys. Rather they noted very interesting 5-fold self-similar structures. Perhaps a discussion under substitution tiling would be more appropriate. As for hype, well, they did choose the term "quasicrystalline tiling", and had they not, the article would not have made nearly the splash it did (regardless of its merit). Predictably, this was distorted in the press, and here we are.

[edit] Aperiodic v/s nonperiodic

As the mathematicians would have it, a set of tiles is aperiodic if all the tilings which it admits are nonperiodic. So 'aperiodic tiling' appears to be a misnomer and use of 'aperiodic' as synonymous to nonperiodic may be a malaproprism. However the physicists' interest is in tilings (and not in tiles) and the context allows to disregard the distinction.

There seems to be a clash between correctness and usage which would not be easily resolved. Perhaps a note should mention it.al 08:58, 1 October 2007 (UTC)