Tag: crystallography

• A new beast: antiferromagnetic quasicrystals

  Scientists have made a new material that is both a quasicrystal and antiferromagnetic — a combination never seen before.

  Quasicrystals are a special kind of solid. Unlike normal crystals, whose atoms are arranged in repeating patterns, quasicrystals have patterns that never exactly repeat but which still have an overall order. While regular crystals have left-right symmetries, quasicrystals have unusual rotational ones.

  For decades, scientists wondered if certain kinds of magnetism, but especially antiferromagnetism, could exist in these strange materials. In all materials the electrons have a property called spin. It’s as if a small magnet is embedded inside each electron. The spin denotes the direction of this magnet’s magnetic field. In ferromagnets, the spins are aligned in a common direction, so the materials are attracted to magnets. In antiferromagnetic materials, the electron spins line up in alternating directions, so their effects cancel out.

  While antiferromagnetism is common in regular crystals, it’s thus far never been observed in a true quasicrystal.

  The new study is the first to show clear evidence of antiferromagnetic order in a real, three-dimensional quasicrystal — one made of gold, indium, and europium. The findings were published in Nature Physics on April 14.

  The team confirmed such a material is real by carefully measuring how its atoms and spins are arranged and by observing how it behaves at low temperatures. Their work shows that even in the weird world of quasicrystals, complex magnetic order is possible, opening the door to new discoveries and technologies.

  The scientists created a new alloy with the formula Au₅₆In_28.5Eu_15.5. This means in 1,000 atoms’ worth of the material, 560 will be gold, 285 will be indium, and 155 will be europium. The composition tells us that the scientists were going for a particularly precise combination of these elements — which they could have known in one of two ways. It might have been trial-and-error*, but that makes research very expensive, or the scientists had reasons to expect antiferromagnetic order would appear in this material.

  They did. Specifically, the team focused on Au₅₆In_28.5Eu_15.5 because of its (i) unique positive Curie-Weiss temperature and (ii) rare-earth content, and (iii) because its structural features matched the theoretical criteria for stable antiferromagnetic order. Previous studies focused on quasicrystals containing rare-earth elements because they often have strong magnetic interactions. However, these compounds typically displayed a negative Curie-Weiss temperature, indicating dominant antiferromagnetic interactions but resulting only in disordered magnetic states.

  A positive Curie-Weiss temperature indicates dominant ferromagnetic interactions. In this case, however, it also suggested a unique balance of magnetic forces that could potentially stabilise antiferromagnetic order rather than spin-glass behaviour. Studies on approximant crystals — periodic structures closely related to quasicrystals — had also shown that both ferromagnetic and antiferromagnetic orders are stabilised only when the Curie-Weiss temperature is positive. In contrast, a negative temperature led to spin-glass states.

  The scientists of the new study noticed that the Au-In-Eu quasicrystal fit into the positive Curie-Weiss temperature category, making it a promising candidate to have antiferromagnetic order.

  For added measure, by slightly altering the composition, e.g. adding an impurity to increase the electron-per-atom ratio, the scientists could make the antiferromagnetic phase disappear, to be replaced by spin-glass behaviour. This sensitivity to electron concentration further hinted that the composition of the alloy was at a sweet spot for stabilising antiferromagnetism.

  Finally, the team had also recently discovered ferromagnetic order in some similar gold-based quasicrystals with rare-earth elements. The success encouraged them to explore the magnetic properties of new compositions, especially those with unusual Curie-Weiss temperatures.

  The Au-In-Eu quasicrystal is also a Tsai-type icosahedral quasicrystal, meaning it features a highly symmetric atomic arrangement. Theoretical work has suggested that such structures could support antiferromagnetic order in the right conditions, especially if the atoms occupied specific sites in the lattice.

  To make the alloy, the scientists used a technique called arc-melting, where highly pure metals are melted together using an electric arc, then quickly cooled to form the solid quasicrystal. To ensure the mixture was even, the team melted and flipped the sample several times.

  Then they used X-ray and electron diffraction to check the atomic arrangement. These techniques passed X-rays and electrons through the material. A detector on the other side picked up the radiation scattered by the material’s atoms and used it to recreate their arrangement. The patterns showed the material was a primitive icosahedral quasicrystal, a structure with 20-sided symmetry and no repeating units.

  The team also confirmed special arrangement of atoms by the way the diffraction patterns followed mathematical rules that are special to quasicrystals. Team members also used a magnetometer to track how much the material was magnetised when exposed to a magnetic field, from temperatures as low as 0.4 K to up to 300 K. Finally they also measured the material’s specific heat, i.e. the amount of heat energy it took to raise its temperature by 1º C. This reading can show signs of magnetic transitions.

  

  To confirm how the spins inside the material were arranged, the team used neutron diffraction. Neutrons are adept at passing through materials and are sensitive to both atoms’ positions and magnetic order. By comparing patterns at temperatures above and below the suspected transition point, they could spot the appearance of new peaks that signal magnetic order.

  This way, the team reported that at 6.5 K, the magnetisation curve showed a sharp change, known as a cusp. This is a classic sign of an antiferromagnetic transition, where the material suddenly changes from being unordered to having a regular up-and-down pattern of spins. The specific heat also showed a sharp peak at this temperature, confirming something dramatic was happening inside the material.

  The scientists also reported that there was no sign of spin-glass behaviour — where the spins are pointing in random directions but unchanging — which is common in other magnetic quasicrystals.

  Below 6.5 K, new peaks appeared in the neutron diffraction data, evidence that the spins inside the material were lining up in the regular but alternating pattern characteristic of antiferromagnetic order. The peaks were also sharp and well-defined, showing the order was long-range, meaning they were there throughout the material and not confined to small patches.

  The team also experimented by adding a small amount of tin to the alloy, which changed the balance of electrons. This little change caused the material to lose its antiferromagnetic order and become a spin glass instead, showing how delicate the balance is between different magnetic states in quasicrystals.

  The findings are important because this is the first time scientists have observed antiferromagnetic order in a real, three-dimensional quasicrystal, settling a long-standing debate. They also open up a new field of study, of quasiperiodic antiferromagnets, and suggest that by carefully tuning the composition, scientists may be able to find yet other types of magnetic order in quasicrystals.

  “The present discovery will stimulate both experimental and theoretical efforts to elucidate not only its unique magnetic structure but also the intrinsic properties of the quasiperiodic order parameter,” the scientists wrote in their paper. “Another exciting aspect of magnetically ordered quasicrystals is their potential for new applications such as functional materials in spintronics” — which use electron spins to store and process information in ultra-fast computers of the future.

  ---

  * Which is not the same as serendipity.

  Featured image credit: Nature Physics volume 21, pages 974–979 (2025).

  2025.07.11

• Why do quasicrystals exist?

  Featured image: An example of zellij tilework in the Al Attarine Madrasa in Fes, Morocco (2012), with complex geometric patterns on the lower walls and a band of calligraphy above. Caption and credit: just_a_cheeseburger (CC BY)

  ---

  ‘Quasi’ means almost. It’s an unfair name for quasicrystals. These crystals exist in their own right. Their name comes from the internal arrangement of their atoms. A crystal is made up of a repeating group of some atoms arranged in a fixed way. The smallest arrangement that repeats to make up the whole crystal is called the unit cell. In diamond, a convenient unit cell is four carbon atoms bonded to each other in a tetrahedral (pyramid-like) arrangement. Millions of copies of this unit cell together make up a diamond crystal. The unit cell of sodium chloride has a cubical shape: the chloride ions (Cl^–) occupy the corners and face centres while the sodium ions (Na⁺) occupy the middle of the edges and centre of the cube. As this cube repeats itself, you get table salt.

  The structure of all crystals thus follows two simple rules: have a unit cell and repeat it. Thus the internal structure of crystals is periodic. For example if a unit cell is 5 nanometres wide, it stands to reason you’ll see the same arrangement of atoms after every 5 nm. And because it’s the same unit cell in all directions and they don’t have any gaps between them, the unit cells fill the space available. It’s thus an exercise in tiling. For example, you can cover a floor of any shape completely with square or triangular tiles (you’ll just need to trim those at the edges). But you can’t do this with pentagonal tiles. If you do, the tiles will have gaps between them that other pentagonal tiles can’t fill.

  Quasicrystals buck this pattern in a simple way: their unit cells are like pentagonal tiles. They repeat themselves but the resulting tiling isn’t periodic. There are no gaps in the crystal either because instead of each unit cell just like the one on its left or right, the tiles sometimes slot themselves in by rotating by an angle. Thus rather than the crystal structure following a grid-like pattern, the unit cells seem to be ordered along curves. As a result, even though the structure may have an ordered set of atoms, it’s impossible to find a unit cell that by repeating itself in a straight line gives rise to the overall crystal. In technical parlance, the crystal is said to lack translational symmetry.

  Such structures are called quasicrystals. They’re obviously not crystalline, because they lack a periodic arrangement of atoms. They aren’t amorphous either, like the haphazardly arranged atoms of glass. Quasicrystals are somewhere in between: their atoms are arranged in a fixed way, with different combinations of pentagonal, octagonal, and other tile shapes that are disallowed in regular crystals, and with the substance lacking a unit cell. Instead the tiles twist and turn within the structure to form mosaic patterns like the ones featured in Islamic architecture (see image at the top).

  

  The discovery of quasicrystals in the early 1980s was a revolutionary moment in the history of science. It shook up what chemists believed a crystal should look like and what rules the unit cell ought to follow. The first quasicrystals that scientists studied were made in the lab, in particular aluminium-manganese alloys, and there was a sense that these unusual crystals didn’t occur in nature. That changed in the 1990s and 2000s when expeditions to Siberia uncovered natural quasicrystals in meteorites that had smashed into the earth millions of years ago. But even this discovery kept one particular question about quasicrystals alive: why do they exist? Both Al-Mn alloys and the minerals in meteorites form in high temperatures and extreme pressures. The question of their existence, more than just because they can, is a question about whether the atoms involved are forced to adopt a quasicrystal rather than a crystal structure. In other words, it asks if the atoms would rather adopt a crystal structure but don’t because their external conditions force them not to.

  ---

  This post benefited from feedback from Adhip Agarwala.

  ---

  Often a good way to understand the effects of extreme conditions on a substance is using the tools of thermodynamics — the science of the conditions in which heat moves from place to another. And in thermodynamics, the existential question can be framed like this, to quote from a June paper in Nature Physics: “Are quasicrystals enthalpy-stabilised or entropy-stabilised?” Enthalpy-stabilised means the atoms of a quasicrystal are arranged in a way where they collectively have the lowest energy possible for that group. It means the atoms aren’t arranged in a less-than-ideal way forced by their external conditions but because the quasicrystal structure in fact is better than a crystal structure. It answers “why do quasicrystals exist?” with “because they want to, not just because they can”. Entropy-stabilised goes the other way. That is: at 0 K (-273.15º C), the atoms would rather come together as a crystal because a crystal structure has lower energy at absolute zero. But as the temperature increases, the energy in the crystal builds up and forces the atoms to adjust where they’re sitting so that they can accommodate new forces. At some higher temperature, the structure becomes entropy-stabilised. That is, there’s enough disorder in the structure — like sound passing through the grid of atoms and atoms momentarily shifting their positions — that allows it to hold the ‘excess’ energy but at the same time deviate from the orderliness of a crystal structure. Entropy stabilisation answers “why do quasicrystals exist?” with “because they’re forced to, not because they want to”.

  In materials science, the go-to tool to judge whether a crystal structure is energetically favourable is density functional theory (DFT). It estimates the total energy of a solid and from there scientists can compare competing phases and decide which one is most stable. If four atoms will have less energy arranged as a cuboid than as a pyramid at a certain temperature and pressure, then the cuboidal phase is said to be more favoured. The problem is DFT can’t be directly applied to quasicrystals because the technique assumes that a given mineral has a periodic internal structure. Quasicrystals are aperiodic. But because scientists are already comfortable with using DFT, they have tried to surmount this problem by considering a superunit cell that’s made up of a large number of atoms or by assuming that a quasicrystal’s structure, while being aperiodic in three dimensions, could be periodic in say four dimensions. But the resulting estimates of the solid’s energy have not been very good.

  In the new Nature Physics paper, scientists from the University of Michigan, Ann Arbor, have reported a way around the no-unit-cell problem to apply DFT to estimate the energy of two quasicrystals. And they found that these quasicrystals are enthalpy-stabilised. The finding answer is a chemistry breakthrough because it raises the possibility of performing DFT in crystals without translational symmetry. Further, by showing that two real quasicrystals are enthalpy-stabilised, chemists may be forced to rethink why almost every other inorganic material does adopt a repeating structure. Crystals are no longer at the centre of the orderliness universe.

  

  The team started by studying the internal structure of two quasicrystals using X-rays, then ‘scooped’ out five random parts for further analysis. Each of these scoops had 24 to 740 atoms. Second, the team used a modified version of DFT called DFT-FE. The computational cost of running DFT scales increases according to the cube of the number of atoms being studied. If studying four atoms with DFT requires X amount of computing power, 24 atoms would require 8,000 times X and 740 atoms would require 400 million times X. Instead the computational cost of DFT-FE scales as the square of the number of atoms, which makes a big difference. Continuing from the previous example, 24 atoms would require 400 times X and 740 atoms would require half a million times X. But the lower computational cost of DFT-FE is still considerable. The researchers’ solution was to use GPUs — the processors originally developed to run complicated video games and today used to run artificial intelligence (AI) apps like ChatGPT.

  The team was able to calculate that the resulting energy estimates for a quasicrystal was off by no more than 0.3 milli-electron-volt (meV) per atom, considered acceptable. They also applied their technique to a known crystal, ScZn₆, and confirmed that its estimate of the energy matched the known value (5-9 meV per atom). They were ready to go now.

  When they applied DFT-FE to scandium-zinc and ytterbium-cadmium quasicrystals, they found clear evidence that they were enthalpy-stabilised. Each atom in the scandium-zinc quasicrystal had 23 meV less energy than if it had been part of a crystal structure. Similarly atoms in the ytterbium-cadmium quasicrystal had roughly 7 meV less each. The verdict was obvious: translational symmetry is not required for the most stable form of an inorganic solid.

  

  The researchers also explored why the ytterbium-cadmium quasicrystal is so much easier to make than the scandium-zinc quasicrystal. In fact the former was the world’s first two-element quasicrystal to be discovered, 25 years ago this year. The team broke down the total energy as the energy in the bulk plus energy on the surface, and found that the scandium-zinc quasicrystal has high surface energy.

  This is important because in thermodynamics, energy is like cost. If you’re hungry and go to a department store, you buy the pack of biscuits that you can afford rather than wait until you have enough money to buy the most expensive one. Similarly, when there’s a hot mass of scandium-zinc as a liquid and scientists are slowly cooling it, the atoms will form the first solid phase they can access rather than wait until they have accumulated enough surface energy to access the quasicrystal phase. And the first phase they can access will be crystalline. On the other hand scientists discovered the ytterbium-cadmium quasicrystal so quickly because it has a modest amount of energy across its surface and thus when cooled from liquid to solid, the first solid phase the atoms can access is also the quasicrystal phase.

  This is an important discovery: the researchers found that a phase diagram alone can’t be used to say which phase will actually form. Understanding the surface-energy barrier is also important, and could pave the way to a practical roadmap for scientists trying to grow crystals for specific applications.

  The big question now is: what special bonding or electronic effects allow atoms to have order without periodicity? After Israeli scientist Dan Shechtman discovered quasicrystals in 1982, he didn’t publish his findings until two years later, after including some authors on his submission to improve its chances with a journal, because he thought he wouldn’t be taken seriously. This wasn’t a silly concern: Linus Pauling, one of the greatest chemists in the history of subject, dismissed Shechtman’s work and called him a “quasi-scientist”. The blowback was so sharp and swift because chemists like Pauling, who had helped establish the science of crystal structures, were certain there was a way crystals could look and a way they couldn’t — and quasicrystals didn’t have the right look. But now, the new study has found that quasicrystals look perfect. Perhaps it’s crystals that need to explain themselves…

  2025.06.26

• The notion of natural quasicrystals is here to stay

  In November 2008, Luca Bindi, a curator at the Universita degli Studi di Firenze, Italy, found that the alloy of aluminium and copper called khatyrkite could be a quasicrystal. Bindi couldn’t be sure because he didn’t have the transmission electron microscope necessary to verify his find, so he couriered two grains of it to a lab in Princeton University. There, physicists Paul Steinhardt – whose name has been associated with the study of quasicrystals since their discovery in 1982 – and Nan Yao made their monumental discovery: the alloy was indeed a quasicrystal, and that meant these abnormal crystal structures could form naturally as well.

  Before 1982, solid substances were either crystalline or amorphous. The atoms or molecules of crystalline substances were neatly stacked in a variety of patterns, but in patterns nonetheless, that were repetitive – whether you moved them to the left or right or rotated them by some amount. In amorphous substances, their arrangement was chaotic. Then, the physicist Dan Shechtman discovered quasicrystals, crystalline solids whose atoms or molecules were arranged in patterns that were orderly but, somehow, not repetitive. It altered the extant paradigm of physical chemistry, overthrowing knowledge a century old and redefining crystallography. Shechtman won a Nobel Prize in chemistry for his work in 2011.

  

  The discovery that khatyrkite did in fact harbor quasicrystals, on New Year’s Day 2009, triggered an expedition to the foot of the Koryak Mountains in eastern Russia in 2011. Steinhardt and Bindi were there, and his team found some strange rocks along a stream 230 km to the south-west of Anadyr, the capital of Chukotka, in which quasicrystal grains were embedded. More fascinating was the quasicrystals’ composition itself, identified as icosahedrite and thought to be of extraterrestrial origins. Steinhardt & co. think it formed in our solar nebula 4.57 billion years ago – when Earth was being formed, too – and got attached to a meteorite that crashed on Earth 15,000 years ago.

  The latest results from this expedition were published in Scientific Reports on March 13. For all its details, the paper remains silent about the ten years of work and dedication consumed in discovering these anomalous crystals in a remote patch of the Russian tundra, about the human experience that fleshed out the discovery’s implications for the birth of the Solar System. Fortunately, Virat Markandeya was loud about it, in the November 2013 issue of Periscope magazine, and well. The piece is a must-read now that the notion of natural quasicrystals is here to stay.

  2015.03.17

• A case of Kuhn, quasicrystals & communication – Part III

  The doctrine of incommensurability arises out of the conflict between two paradigms and the faltering of communications between the two adherent factions.

  According to Kuhn, scientists are seldom inclined to abandon the paradigm at the first hint of crisis – as elucidated in the previous section – and instead denounce the necessity for a new paradigm. However, these considerations aside, the implications for a scientist who proposes the introduction of a new paradigm, as Shechtman did, are troublesome.

  Such a scientist will find himself ostracized by the community of academicians he belongs to because of the anomalous nature of his discovery and, thus, his suddenly questionable credentials. At the same time, because of such ostracism, the large audience required to develop the discovery and attempt to inculcate its nature into the extant paradigm becomes inaccessible.

  As a result, there is a communication breakdown between the old faction and the new faction, whereby the former rejects the finding and continues to further the extant paradigm while the latter rejects the paradigm and tries to bring in a new one.

  Incommensurability exists only during the time of crisis, when a paradigm shift is foretold. A paradigm shift is called so because there is no continuous evolution from the old paradigm to the new one. As Kuhn puts it (p. 103),

  … the reception of a new paradigm often necessitates a redefinition of the corresponding science.

  For this reason, what is incommensurable is not only the views of warring scientists but also the new knowledge and the old one. In terms of a finding, the old knowledge could be said to be either incomplete or misguided, whereas the new one could be remedial or revolutionary.

  In Shechtman’s case, because icosahedral symmetries were altogether forbidden by the old theory, the new finding was not remedial but revolutionary. Therefore, the new terms that the finding introduced were not translatable in terms of the old one, leading to a more technical form of communication breakdown and the loss of the ability of scientists to predict what could happen next.

  A final corollary of the doctrine is that because of the irreconcilable nature of the new and old knowledge, its evolution cannot be held to be continuous, only contiguous. In this sense, knowledge becomes a non-cumulative entity, one that cannot have been accumulated continuously over the centuries, but one that underwent constant redefinition to become what it is today.

  As for Dan Shechtman, the question is this: Does the media’s portrayal of the crisis period reflect any incommensurability (be it in terms of knowledge or communication)?

  How strong was the paradigm shift?

  In describing the difference between “seeing” and “seeing as”, Kuhn speaks about two kinds of incommensurability as far as scientific knowledge is concerned. Elegantly put as “A pendulum is not a falling stone, nor is oxygen dephlogisticated air,” the argument is that when a paradigm shift occurs, the empirical data will remain unchanged even as the relationship between the data changes. In Shechtman’s and Levine’s cases, the discovery of “forbidden” 3D icosahedral point symmetry does not mean that the previous structures are faulty but simply that the new structure is now one of the possibilities.

  However, there is some discrepancy regarding how much the two paradigms are really incommensurable. For one, Kuhn’s argument that an old paradigm and a new paradigm will be strongly incommensurable can be disputed: he says that during a paradigm shift, there can be no reinterpretation of the old theory that can transform to being commensurable with the new one.

  However, this doesn’t seem to be the case: five-fold axes of symmetry were forbidden by the old theory because they had been shown mathematically to lack translational symmetry, and because the thermodynamics of such a structure did not fall in line with the empirical data corresponding to crystals that were perfectly crystalline or perfectly amorphous.

  Therefore, the discovery of QCs established a new set of relationships between the parameters that influenced the formation of one crystal structure over another. At the same time, they did permit a reinterpretation of the old theory because the finding did not refute the old laws – it just introduced an addition.

  For Kuhn to be correct a paradigm shift should have occurred that introduced a new relationship between different bits of data; in Shechtman’s case, the data was not available in the first place!

  Here, Shechtman can be attributed with making a fantastic discovery and no more. There is no documented evidence to establish that someone observed QC before Shechtman did but interpreted it according to the older paradigm.

  In this regard, what is thought to be a paradigm shift can actually be argued to be an enhancement of the old paradigm: no shift need have occurred. However, this was entirely disregarded by science journalists and commentators such as Browne and Eugene Garfield, who regarded the discovery of QCs as simply being anomalous and therefore crisis-prompting, indicating a tendency to be historicist – in keeping with the antirealism argument against scientific realism as put forth by Richard Boyd.

  Thus, the comparison to The Structure that held up all this time fails.

  There are many reasons why this could have been so, not the least of which is the involvement of Pauling and his influence in postponing the announcement of the discovery (Pauling’s credentials were, at the time, far less questionable than Shechtman’s were).

  

  As likely as oobleck

  Alan I. Goldman, a professor of physics at the Iowa State University, wrote in the 84^th volume of the American Scientist,

  Quasicrystals … are rather like oobleck, a form of precipitation invented by Dr. Seuss. Both the quasicrystals and the oobleck are new and unexpected. Since the discovery of a new class of materials is about as likely as the occurrence of a new form of precipitation, quasicrystals, like oobleck, suffered at first from a credibility problem.

  There were many accomplished chemists who thought that QCs were nothing more than as-yet not fully understood crystal structures, and some among them even believed that QCs were an anomalous form of glass.

  The most celebrated among those accomplished was Linus Pauling, who died in 1994 after belatedly acknowledging the existence of QCs. It was his infamous remark in 1982 that bought a lot of trouble for Shechtman, who was subsequently asked to leave the research group because he was “bringing disgrace” on its members and the paper he sought to publish was declined by journals.

  Perhaps this was because he took immense pride in his works and in his contributions to the field of physical chemistry; otherwise, his “abandonment” of the old paradigm would have come easier – and here, the paradigm that did include an observation of QCs is referred to as old.

  In fact, Pauling was so adamant that he proposed a slew of alternate crystal structures that would explain the structure of QCs as well as remain conformant with the old paradigm, with a paper appearing in 1988, long after QCs had become staple knowledge.

  Order and periodicity

  Insofar as the breakdown in communication is concerned, it seems to have stemmed from the tying-in of order and periodicity: crystallography’s handing of crystalline and amorphous substances had ingrained into the chemist’s psyche the coexistence of structures and repeatability.

  Because the crystal structures of QCs were ordered but not periodical, even those who could acknowledge their existence had difficulty believing that QCs “were just as ordered as” crystals were, in the process isolating Shechtman further.

  John Cahn, a senior crystallographer at NBS at the time of the fortuitous discovery, was one such person. Like Pauling, Cahn also considered possible alternate explanations before he could agree with Shechtman and ultimately co-author the seminal PRL paper with him.

  His contention was that forbidden diffraction patterns – like the one Shechtman had observed – could be recreated by the superposition of multiple allowed but rotated patterns (because of the presence of five-fold symmetry, the angle of rotation could have been 72°).

  

  This was explained through a process called twinning, whereby the growth vector of a crystal, during its growth phase, could suddenly change direction without any explanation or prior indication. In fact, Cahn’s exact response was,

  Go away, Danny. These are twins and that’s not terribly interesting.
  

  This explanation involving twinning was soon adopted by many of Shechtman’s peers, and he was repeatedly forced to return with results from the diffraction experiment to attempt to convince those who disagreed with the finding. His attempts were all in vain, and he was eventually dismissed from the project group at NBS.

  Conclusion

  All these events are a reflection of the communication breakdown within the academic community and, for a time, the two sides were essentially Shechtman and all the others.

  The media portrayal of this time, however, seems to be completely factual and devoid of deduction or opining because of the involvement of the likes of Pauling and Cahn, who, in a manner of speaking, popularized the incident among media circles: that there was a communication breakdown became ubiquitous fact.

  Shechtman himself, after winning the Nobel Prize for chemistry in 2011 for the discovery of QCs, admitted that he was isolated for a time before acceptance came his way – after the development of a crisis became known.

  At the same time, there is the persisting issue of knowledge as being non-accumulative: as stated earlier, journalists have disregarded the possibility, not unlike many scientists, unfortunately, that the old paradigm did not make way for a new one as much as it became the new one.

  That this was not the focus of their interest is not surprising because it is a pedantic viewpoint, one that serves to draw attention to the “paradigm shift” not being “Kuhnian” in nature, after all. Just because journalists and other writers constantly referred to the discovery of QCs as being paradigm-shifting need not mean that a paradigm-shift did occur there.

  2012.10.23

• A case of Kuhn, quasicrystals & communication – Part II

  Did science journalists find QCs anomalous? Did they report the crisis period as it happened or as an isolated incident? Whether they did or did not will be indicative of Kuhn’s influence on science journalism as well as a reflection of The Structure’s influence on the scientific community.

  In the early days of crystallography, when the arrangements of molecules was thought to be simpler, each one was thought to occupy a point in two-dimensional (2D) space, which were then stacked one on top of another to give rise to the crystal. However, as time passed and imaginative chemists and mathematicians began to participate in the attempts to deduce perfectly the crystal lattice, the idea of a three-dimensional (3D) lattice began to catch on.

  At the same time, scientists also found that there were many materials, like some powders, which did not restrict their molecules to any arrangement and instead left them to disperse themselves chaotically. The former were called crystalline, the latter amorphous (“without form”).

  All substances, it was agreed, had to be either crystalline – with structure – or amorphous – without it. A more physical definition was adopted from Euclid’s Stoicheia (Elements, c. 300 BC): that the crystal lattice of all crystalline substances had to exhibit translational symmetry and rotational symmetry, and that all amorphous substances couldn’t exhibit either.

  An arrangement exhibits translational symmetry if it looks the same after being moved in any direction through a specific distance. Similarly, rotational symmetry is when the arrangement looks the same after being rotated through some angle.)

  In an article titled ‘Puzzling Crystals Plunge Scientists Into Uncertainty’ published in The New York Times on July 30, 1985, Pulitzer-prize winning science journalist Malcolm W Browne wrote that “the discovery of a new type of crystal that violates some of the accepted rules has touched off an explosion of conjecture and research…” referring to QCs.

  

  Paper a day on the subject

  In the article, Browne writes that Shechtman’s finding (though not explicitly credited) has “galvanized microstructure analysts, mathematicians, metallurgists and physicists in at least eight countries.”

  This observation points at the discovery’s anomalous nature since, from an empirical point of view, Browne suggests that such a large number of scientists from fields as diverse have not come together to understand anything in recent times. In fact, he goes on to remark that according to one estimate, a paper a day was being published on the subject.

  Getting one’s paper published by an academic journal worldwide is important to any scientist because it formally establishes primacy. That is, once a paper has been published by a journal, then the contents of the paper are attributed to the paper’s authors and none else.

  Since no two journals will accept the same paper for publication (a kind of double jeopardy), a paper a day implies that distinct solutions were presented each day. Therefore, Browne seems to claim in his article, in the framework of Kuhn’s positions, that scientists were quite excited about the discovery of a phenomenon that violated a longstanding paradigm.

  Shechtman’s paper had been published in the prestigious Physical Review Letters, which is in turn published by the American Physical Society from Maryland, USA, in the 20^th issue of its 53^rd volume, 1984 – but not without its share of problems.

  Istvan Hargittai, a reputed crystallographer with the Israel Academy of Sciences and Humanities, described a first-hand account of the years 1982 to 1984 in Shechtman’s life in the April 2011 issue of Structural Chemistry. In these accounts, he says that,

  Once Shechtman had completed his experiment, he became very lonely as every scientific discoverer does: the discoverer knows something nobody else does.

  In Shechtman’s case, however, this loneliness was compounded by two aspects of his discovery that made it difficult for him to communicate with his peers about it. First: To him, it was such an important discovery that he wanted desperately to inquire about its possibilities to those established in the field – and the latter dismissed his claims as specious.

  Second: the fact that he couldn’t conclusively explain what he himself had found troubled him, kept him from publishing his results.

  At the time, Hargittai was a friend of a British crystallographer named Alan Mackay, from the Birkbeck College in London. Mackay had, a few years earlier, noted the work of mathematician Roger Penrose, who had created a pattern in which pentagons of different sizes were used to tile a 2D space completely (Penrose had derived inspiration from the work of the 16^th century astronomer Johannes Kepler).

  In other words, Penrose had produced theoretically a planar version of what Shechtman was looking for, what would help him resolve his personal crisis. Mackay, in turn, had attempted to produce a diffraction pattern simulated on the Penrose tiles, assuming that what was true for 2D-space could be true for 3D-space as well.

  

  By the time Mackay had communicated this development to Hargittai, Shechtman had – unaware of them – already discovered QCs.

  There was another investigation ongoing at the University of Pennsylvania’s physics department: Dov Levine, pursuing his PhD under the guidance of Paul Steinhardt, had developed a 3D model of the Penrose tiles – again, unaware of Shechtman’s and Mackay’s works.

  Thus, it is conspicuous how the anomalous nature of discoveries – which are unprecedented by definition because, otherwise, they would be expected – facilitates a communication-breakdown within the scientific community. In the case of Levine, who was eager to publish his findings, Steinhardt advised caution to avoid the ignominy that might arise out of publishing findings that are not fully explicable.

  In the meantime, Shechtman had found an interested listener in Ilan Blech, another crystallographer at NBS. They prepared a paper together to send to the Journal of Applied Physics in 1984 after deciding that it was imperative to get across to as many scientists as possible in the search for an explanation for the structure of QCs.

  However, since they had no explanation of their own, the paper had to be buried “under a mountain of information about alloys,” which prompted the Journal to write back saying the paper “would not interest physicists.”
  

  Shechtman and Blech realized that, as a consequence of reporting such a result, they would have to spruce up its presentation. Shechtman invited veteran NBS crystallographer John Cahn, and Cahn in turn invited Denis Gratias, a French crystallographer, to join the team.

  Even though Cahn had been sceptical of the possibility of QCs, he had since changed his mind in the last two years, and his presence awarded some credibility to the contents of the paper. After Gratias restructured the mathematics in the paper, it was finally accepted for publication in the Physical Review Letters on November 12, 1984.

  

  And by the time Browne’s article appeared a year later, it is safe to assume that at least 50-70 papers on the subject were published in the period. Whether this was a rush to accumulate anomalies or to discredit the finding is immaterial: the threat to the existing paradigm was perceptible and scientists felt the need to do something about it; and Browne’s noting of the same is proof that science journalists noted the need, too.

  In fact, how much of an anomaly is a finding that has been accepted for publication? Because after it has been carefully vetted and published, it becomes as good as fact: other scientists can now found their work upon on it, and at the time of publication of their papers, cite the parent paper as authority.

  However, it must be noted that there are important exceptions, such as the infamous Fleischmann-Pons experiment in cold fusion in 1989-1990. For these reasons, let it be that a paradigm is considered to have entered a crisis period only after it is established that it cannot be “tweaked” after each discovery and allowed to continue.

  Three years of falsifications

  Browne, too, seems to conclude that despite a definite discovery having been made three years earlier,

  … only recently has experimental evidence overwhelmed the initial skepticism of the scientific community that such a form of matter could exist.

  For three years, the community could not allow a discovery to pass, and subjected it repeatedly to tests of falsifications. A similar remark comes from science writer and crystallographer Paul Steinhardt, Levine’s PhD mentor, who, in a paper titled ‘New perspectives on forbidden symmetries, quasicrystals and Penrose tilings’, remarked upon the need for “a new appreciation for the subtleties of crystallographically forbidden symmetries.”

  Shechtman’s QCs exhibited rotational symmetry but not a translational one. In other words, they demanded to be placed squarely between crystalline and amorphous substances, sending researchers scurrying for an explanation.

  In a period of such turmoil, Browne’s article states that some researchers were willing to consider the arrangement as existing in six-dimensional (6D) hyperspace rather than in 3D space-time.

  

  Now, someone within the community had considered physical hyperspace to be an explanation way back in 1985. Even though mathematical hyperspace as a theory had been around since the days of Bernhard Riemann (Habilitationsschrift, 1854) and Ludwig Schläfli (Theorie der vielfachen Kontinuität, 1852), the notion of physical hyperspatial theory with a correspondence to physical chemistry is still nascent at best.

  Therefore, Browne’s suggestion only seems to supplant his narrative of intellectual turbulence, that scientists had stumbled upon a phenomenon so anomalous that it alone was prompting crisis.

  Conclusion

  Did science journalists find QCs anomalous? Yes, they did. Browne, Hargittai and Steinhardt, amongst others, were quick to identify the anomalous nature of the newly discovered material and point it out through newspaper reports and articles published within the scientific community.

  Thomas Kuhn’s position that scientists will attempt to denounce a paradigm-shift-inducing theory before they themselves are forced to shift is reflected in the writers’ accounts of Dan Shechtman in the days leading up to and just after his discovery.

  Did they, the journalists, report the crisis period as it happened or as an isolated incident? That they could identify the onset of a crisis as it happened indicates that they did recognize it for what it was. However, it remains to be seen whether these confirmations validate Kuhn’s hypothesis in their entirety.

  2012.10.21