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Νόμπελ Χημείας 2011

Στον Ντάνιελ Σέχτμαν το Νόμπελ Χημείας

ΕΛΕΥΘΕΡΟΤΥΠΙΑ, 5.10.11

Ο Ισραηλινός επιστήμονας Ντάνιελ Σέχτμαν βραβεύτηκε με το φετινό Νόμπελ Χημείας για την ανακάλυψη της δομής των ημικρυστάλλων, ενός «συναρπαστικού μωσαϊκού ατόμων που ποτέ δεν επαναλαμβάνεται ίδιο», σύμφωνα με την ανακοίνωση της Επιτροπής Νόμπελ.


Η Βασιλική Σουηδική Ακαδημία Επιστημών κάνει λόγο στην ανακοίνωσή της για το ότι η ανακάλυψη του Σέχτμαν το 1982, άλλαξε ριζικά τον τρόπο που οι επιστήμονες αντιλαμβάνονται τη στερεά ύλη.

Στις 8 Απριλίου 1982, ο Σέχτμαν ανακάλυψε έναν κρύσταλλο μέσα στον οποίο "τα άτομα ήταν συγκεντρωμένα μ’ έναν τρόπο, ο οποίος ποτέ δεν επαναλαμβάνεται", αντίθετα με τους νόμους της φύσης, σύμφωνα με τον εκπρόσωπο της Ακαδημίας. Αυτή η ανακάλυψη, ορίστηκε ως "ημικρύσταλλοι", οι οποίοι θυμίζουν τα "εντυπωσιακά μωσαϊκά του αραβικού κόσμου".

Ο Σέχτμαν γεννήθηκε το 1941 στο Τελ Αβίβ και είναι διακεκριμένος καθηγητής στο Ισραηλινό Ινστιτούτο Τεχνολογίας της Χάιφα.

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Νομπέλ Χημείας στα ατομικά μωσαϊκά.

Νομπέλ Χημείας στα ατομικά μωσαϊκά.Τους ημικρυστάλλους ανακάλυψε
ο φετινός τιμώμενος.

Τ. Καφαντάρης,
ΤΟ ΒΗΜΑ, 5.10.11

Με μωσαϊκά της Αλάμπρα μοιάζουν
οι ημικρύσταλλοι

Στοκχόλμη

Η Βασιλική Σουηδική Ακαδημία Επιστημών ανακοίνωσε σήμερα ότι το εφετινό βραβείο Νομπέλ Χημείας – ύψους 10 εκατομμυρίων σουηδικών κορωνών, ήτοι ενός περίπου εκατ. ευρώ – απονέμεται στον καθηγητή επιστήμης υλικών του ισραηλιτικού πολυτεχνείου Technion, Ντάν Σέχτμαν (Dan Shechtman). Ο λόγος;
Η εκ μέρους του ανακάλυψη ενός νέου τύπου κρυστάλλων, των λεγόμενων ημικρυστάλλων (quasicrystals).

Κρύσταλλοι πενταπλής συμμετρίας

Συνέβη από έναν… μη χημικό… όταν δεν έπρεπε: Τον Απρίλιο του 1982, ο μηχανολόγος και μεταλλογράφος Ντάν Σέχτμαν βρισκόταν σε εκπαιδευτική άδεια από το πανεπιστήμιο John Hopkins των ΗΠΑ (NBS). Το πρωί της 8ης Απριλίου κοίταξε στο ηλεκτρονικό του μικροσκόπιο έναν κρύσταλλο από ταχέως ψυχθέν κράμα αλουμινίου και μαγγανίου και… καθάρισε τα γυαλιά του. Ξανακοίταξε και σιγουρεύτηκε ότι αυτό που έβλεπε ήταν αντίθετο στο κλασικό «θεώρημα περιορισμού» της κρυσταλλογραφίας.
Δηλαδή, ενώ κατά το θεώρημα αυτό οι κρύσταλλοι μπορούν να εμφανίζουν περιοδική συμμετρία κατά τη διάταξη των ατόμων τους (διπλή, τριπλή, τετραπλή ή εξαπλή συμμετρία εκ περιστροφής), ο κρύσταλλος που έβλεπε εμφάνιζε πενταπλή συμμετρία (απεριοδική). Ταραγμένος, ο Σέχτμαν άρχισε να κάνει μετρήσεις και να κρατάει σημειώσεις. Διαπίστωσε ότι η αναλογία των αποστάσεων μεταξύ των ατόμων του περίεργου αυτού κρυστάλλου σχετιζόταν με τον περίφημο Χρυσό Λόγο του Πυθαγόρα.

Αμφισβήτηση και επιμονή

Αυτό που επακολούθησε, αρχικά, ήταν αυτό που συχνότατα συμβαίνει σε όσους τολμούν να αμφισβητήσουν την καθεστώσα γνώση: Όταν ο Σέχτμαν έγραψε εργασία με τα ευρήματά του, του ζητήθηκε να παραιτηθεί από το εργαστήριο όπου εργαζόταν. «Γνώριζα ότι το σχήμα της περίθλασης δεν οφειλόταν σε διδύμους (που προκύπτουν από μια συνήθη κρυσταλλική ατέλεια)», δήλωσε σε κατοπινή συνέντευξή του, «αλλά δεν είχα καμία εξήγηση για το τι πραγματικά συνέβαινε».

Μη μπορώντας να θεμελιώσει θεωρητικά τα πειραματικά του δεδομένα, πιθανότατα θα είχε πέσει στην αφάνεια αν δεν τύχαινε να δείξει την εργασία του στον John Cahn, εξέχοντα ερευνητή στην επιστήμη των υλικών. Ακολουθώντας τις συμβουλές του Cahn και του Denis Gratias – ειδικού στη μαθηματική κρυσταλλογραφία στο Εθνικό Κέντρο Επιστημονικών Ερευνών (CNRS) της Γαλλίας – ο Σέχτμαν και ο συνάδελφός του στο Technion, Άιλαν Μπλεχ (Ilan Blech) υπέβαλαν από κοινού στο περιοδικό Physical Review Letters, τον Οκτώβριο του 1984, μια αναθεωρημένη εκδοχή της εργασίας. Δημοσιεύθηκε τον Νοέμβριο του 1984, περισσότερα από δύο χρόνια μετά το αρχικό πείραμα του Σέχτμαν.

Αναγνώριση και τιμές

Από τότε, η εργασία αυτή έχει ανεβεί στην 8η θέση παγκοσμίως των δημοσιεύσεων αναφοράς (most cited). Ερευνητές από κάθε μήκος και πλάτος της Γης αποδύθηκαν σε έναν αγώνα δρόμου για την διερεύνηση και υλοποίηση τέτοιων απεριοδικών κρυστάλλων, των «ημικρυστάλλων» ή «οιωνεί κρυστάλλων» (quasicrystals) όπως επικράτησε να λέγονται, μολονότι η Διεθνής Ένωση Κρυσταλλογράφων (IUC) τους ενέταξε επίσημα στους κρυστάλλους.

Μέχρι στιγμής, οι ερευνητές που ακολούθησαν τα ίχνη του Σέχτμαν έχουν καταφέρει να δομήσουν εργαστηριακά εκατοντάδες νέα είδη ημικρυστάλλων, άλλους με διεδρική συμμετρία και άλλους με εικοσαεδρική. Σαν να μην έφτανε όμως αυτό, εντόπισαν σε ποταμό της Ρωσίας και ορυκτά που εμπεριέχουν φυσικά σχηματισμένους ημικρυστάλλους. Τέλος, μία σουηδική εταιρεία εντόπισε ημικρυστάλλους σε σε ένα είδος ατσαλιού, όπου η παρουσία τους καταλήγει να ενισχύει το ατσάλι. Η πρακτική εφαρμογή του ευρήματος του Σέχτμαν έχει ήδη αρχίσει, με πρώτους αποδέκτες του τους πετρελαιοκινητήρες και τα τηγάνια της κουζίνας. Ο 70χρονος σήμερα Ντάνιελ Σέχτμαν δικαίως επιβραβεύθηκε ως ο άνθρωπος που… δικαίωσε τον Πυθαγόρα.

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Στον Ισραηλινό Ντάνιελ Σέχτμαν το Νόμπελ Χημείας

ΚΑΘΗΜΕΡΙΝΗ, 5.10.11

Η Επιτροπή των Βραβείων Νόμπελ απένειμε τον ομώνυμο τίτλο στο πεδίο της Χημείας στον Ισραηλινό επιστήμονα για τις ανακαλύψεις του στο πεδίο της ατομικής δομής, οι οποίες ήταν καινοφανείς και προκάλεσαν αντιδράσεις.

Σύμφωνα με την ανακοίνωση, ο Σέχτμαν ανακάλυψε ημικρυστάλλους, που μοιάζουν με «συναρπαστικά μωσαϊκά του αραβικού κόσμου» και τα οποία ποτέ δεν επαναλαμβάνονται.
Μέχρι την ανακάλυψη αυτή, οι επιστήμονες θεωρούσαν ότι οι ακολουθίες ατόμων μέσα στους κρυστάλλους έπρεπε να επαναλαμβάνονται.

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Israeli Scientist Wins Nobel Prize for Chemistry

By KENNETH CHANG,

The New York Times, October 5, 2011

An Israeli scientist won this year’s Nobel Prize in Chemistry for discovering a material in which atoms were packed together in a well-defined pattern that never repeats.

Recent Nobel prizes have generally split credit for scientific advances among two or three people, but this year’s chemistry prize and accompanying 10 million Swedish kronor ($1.4 million) went to a single scientist: Daniel Shechtman, 70, a professor of materials science at Technion-Israel Institute of Technology. Dr. Shechtman is also a professor
at Iowa State University and a researcher at the Department of Energy’s Ames Laboratory.

The citation from the Royal Swedish Academy of Sciences states simply, “for the discovery of quasicrystals.”

Such regular but nonrepeating patterns, defined by precise rules, have been known in mathematics since antiquity, and medieval Islamic artists made decorative, nonrepeating tile mosaics, but it was thought impossible in the packing of atoms.

Yet Dr. Shechtman discovered the same type of structure in a mix of aluminum and manganese. During a sabbatical in the United States at the National Bureau of Standards, now known as the National Institute of Standards and Technology, he took a molten glob of the metals and chilled it rapidly. The expectation was that the atoms would have been a random jumble, like glass. Yet when he examined his metal with an electron microscope, Dr. Shechtman found that the atoms were not random.

His notebook recorded the exact date: April 8, 1982.

Scientists believed that crystals in materials all contained repeating patterns. For example, a square lattice has fourfold symmetry. Rotate it by 90 degrees, and it looks identical. A repeating lattice with fivefold symmetry, however, is impossible. On that morning in 1982, the electrons Dr. Shechtman bounced off his aluminum-manganese alloy formed a pattern that indicated tenfold symmetry. Dr. Shechtman himself could not quite believe it. He wrote in his notebook, “10 Fold???”

While a periodic lattice could not produce that pattern, a quasicrystal could.

It took years for Dr. Shechtman to persuade others.

During the announcement, the Nobel committee noted that one colleague said, “Go away, Danny” and that he was even asked to leave the research group. Many scientists — notably Linus Pauling, the Nobel-winning giant of chemistry — argued vehemently that Dr. Shechtman’s data could be explained by defects within ordinary periodic crystals.

“That must have been intimidating,” said Nancy Jackson, president of the American Chemical Society. “When he first discovered these materials nobody thought they could exist. It was one of these great scientific stories that his fellow scientists thought was impossible, but through time, people came to realize he was right.”

Even the definition of crystal had to be redefined. Previously, a crystal had “a regularly ordered, repeating three-dimensional pattern,” according to the International Union of Crystallography. The new definition, adopted in 1992, states that a crystal is simply a solid with a “discrete diffraction diagram” — that is, something that produces patterns like Dr. Shechtman saw.

That leaves the door open for yet more different kinds of crystals in the future.

Quasicrystals have since been found in many other materials, including a naturally occurring mineral from a Russian river. Materials scientists have been exploring quasicrystals because of their distinct properties. One kind of highly resilient steel, consisting of hard steel quasicrystals embedded within softer steel, is now used in razor blades and thin needles for eye surgery.

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Nobel Prize in Chemistry 2011 – live blog

by Ian Sample, 5 October 2011, guardian.co.uk

This year’s Nobel Prize in Chemistry has been won by Daniel Shechtman for the discovery of quasicrystals

A quasicrystal 

A silver/aluminium quasicrystal of the type discovered by Nobel prizewinner Daniel Shechtman. Photograph: Wikimedia Commons

2.52pm: Blogger Derek Lowe recalls the furore that greeted Shechtman’s claims of five-fold symmetry in metal alloys (quasicrystals):

I was in grad school when the result came out, and I well remember the stir it caused. Just publishing the result took a lot of nerve, since every single crystallographer in the world would tell you that if they knew one thing about their field, it was that you couldn’t have something like this.

As it turned out, these issues had already been well explored by two different groups: medieval Islamic artists and mathematicians. It turns out that what looks like unallowable symmetry in two (or three) dimensions works out just fine in higher-dimensional spaces, and these theoretical underpinnings were actually a lot of help in the debates that followed.

2.28pm: Dr Andrew Goodwin at Oxford University says Shechtman’s Nobel Prize is "fantastic recognition of the continued impact of fundamental research into the structure of materials":

For the last century, our understanding of the arrangement of atoms in materials – from DNA to superconductors – has been built on the rules of crystallography: rules which assume atoms are arranged like tiles in a regular, repeating arrangement.

When studying a series of alloyed metals, Professor Shechtman showed how nature can and does break these rules by including pentagon-like symmetries which prevent the atomic ’tiles’ from ever repeating. Instead the atoms in these alloys follow the same remarkable "quasi-periodic" patterns discovered centuries ago by Islamic artists.

Shechtman’s quasi-crystals are now widely used to improve the mechanical properties of engineering materials and are the basis of an entirely new branch of structural science. If there is one particular lesson we are taking from his research it is not to underestimate the imagination of nature herself.

1.24pm: "A good scientist is a humble scientist," says Shechtman in an interview recorded for Nobelprize.org earlier today.

1.20pm: I’ve just got off the phone to Roger Penrose of Penrose tiling fame, asking for his reaction to today’s prize announcement. More to follow, but he mentioned that way back in the 16th century Johannes Kepler provides an illustration of a pattern very close to that of quasicrystals in his Mysterium Cosmographicum.

1.09pm: Here’s a great article by mathematician Marjorie Senechal explaining quasicrystals. (Thanks @mkd)

1.01pm: Our heartfelt thanks to chemistry graduate @LV09 who provides this potted guide to crystallography and quasicrystals:

Crystallography is essentially the study of the arrangement of atoms in solids (in their crystal form at least).

It is predominantly carried out by x-ray diffraction (there are other types) where an x-ray is shone at a crystal sample of the substance and the resulting pattern can be used to determine the arrangement of the atoms in the substance.

One part of determining the structure depends on the various degrees of symmetry, such as rotational and translational, (bear with me here) in the structure. Part of this is due to the crystal structure being ordered and periodic. Crystallographic restriction theory (I’ve lost some of you now, haven’t I) states that crystals can only have symmetry’s of the order of 2,3,4 and 6.

Quasicrystals, when discovered back in the 1980s (they were observed before but either ignored or explained away), were found to be have an order of symmetry of 5, and were shown to be order but not periodic.

The discovery essentially opened up a whole new avenue of understanding of crystallography.

12.47pm: Shechtman is quoted on PhysOrg.com saying double Nobel prizewinner Linus Pauling was distinctly sceptical about his work:

He would stand on those platforms and declare, "Danny Shechtman is talking nonsense. There is no such thing as quasicrystals, only quasi-scientists."

12.42pm: There’s a more user-friendly guide to quasicrystals in a journal called Physical Review Focus: "Quasicrystals are unusual metallic alloys whose atoms are arranged in orderly patterns that are not quite crystalline …"

12.37pm: For a no-holds-barred explanation of what quasicrystals are and what makes them an entirely novel form of matter, try here. Less cerebrally, check out these astounding images of quasicrystals.

 12.27pm: Shechtman told Associated Press: "It feels wonderful."

Out of nearly 2,000 respondents, 67% say they hadn’t heard of quasicrystals until today.

12.12pm: Do quasicrystals have any practical purpose?

Following Shechtman’s discovery, scientists have produced other kinds of quasicrystals in the lab and discovered naturally occurring quasicrystals in mineral samples from a Russian river. A Swedish company has also found quasicrystals in a certain form of steel, where the crystals reinforce the material like armour. Scientists are currently experimenting with using quasicrystals in different products such as frying pans and diesel engines.

11.30am: From Twitter:

@ag_smaoineamh has this photo of quasicrystal Penrose tiling at Trinity College science gallery.

11.28am: Comments from the great and good have begun to arrive. This from Professor David Phillips, president of the Royal Society of Chemistry:

Quasicrystals are a fascinating aspect of chemical and material science – crystals that break all the rules of being a crystal at all!

You can normally explain in simple terms where in a crystal each atom sits – they are very symmetrical. With quasicrystals, that symmetry is broken: there are regular patterns in the structure, but never repeating.

They’re quite beautiful, and have potential applications in protective alloys and coatings. The award of the Nobel Prize to Danny Shechtman is a celebration of fundamental research.

On the morning of 8 April 1982, an image counter to the laws of nature appeared in Daniel Shechtman’s electron microscope. In all solid matter, atoms were believed to be packed inside crystals in symmetrical patterns that were repeated periodically over and over again. For scientists, this repetition was required in order to obtain a crystal.

Shechtman’s image, however, showed that the atoms in his crystal were packed in a pattern that could not be repeated. Such a pattern was considered just as impossible as creating a football using only six-cornered polygons, when a sphere needs both five- and six-cornered polygons. His discovery was extremely controversial. In the course of defending his findings, he was asked to leave his research group. However, his battle eventually forced scientists to reconsider their conception of the very nature of matter.

11.02am: I just reached Daniel Shechtman on the phone. He said: "I can’t talk right now. I am on the phone to Stockholm." I will talk to him later in the day. Questions?

10.59am: Daniel Shechtman describes quasicrystals last year:

10.56am: From the twittersphere:

Twitter icon

@simon_frantz writes: When Daniel Shechtman made his qusaicrystal disc. he said to himself "Eyn chaya kazo"/"There can be no such creature"

He adds:

Twitter icon

In the course of defending his findings, Shechtman was asked to leave his research group.

10.50am: From the Nobel committee material:

When Daniel Shechtman entered the discovery awarded with the Nobel Prize in Chemistry 2011 into his notebook, he jotted down three question marks next to it. The atoms in the crystal in front of him yielded a forbidden symmetry. It was just as impossible as a football – a sphere – made of only six-cornered polygons. Since then, mosaics with intriguing patterns and the golden ratio in mathematics and art have helped scientists to explain Shechtman’s bewildering observation.

10.48am: The prize has gone to Daniel Shechtman at Technion – Israel Institute of Technology, Haifa, Israel "for the discovery of quasicrystals"

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Impossible crystals snag chemistry Nobel

Daniel Shechtman takes award for doggedly pursuing quasicrystals.

Richard Van Noorden, NATURE, 5.10.11

A materials scientist who discovered crystals with structures that many believed to be impossible — and who stubbornly held his ground against fierce opposition — has claimed this year’s Nobel Prize in Chemistry.

Daniel Shechtman of the Technion Israel Institute of Technology in Haifa was awarded the prize for his 1982 discovery1 of quasicrystals: materials with a mosaic-like, never-quite-repeating atomic structure that defied the textbooks of the time, existing only as mathematical curios. "It took an enormous amount of courage for Danny to stick to his claim," says Veit Elser, a physicist at Cornell University in Ithaca, New York.

It took two years for Shechtman to get his discovery published. His work was scorned by luminaries including double-Nobel-prizewinning chemist Linus Pauling, but after it was published, other examples of the crystals flooded in from around the globe. In 2009, researchers reported finding the quasicrystal structure in an alloy of aluminium, copper and iron, acquired by an Italian museum in 1990 but reported to have come from 200-million-year-old rocks in the Koryak Mountains in Russia2.

"This is an award that we’ve been expecting for 25 years now — I’ve been sending a recommendation letter to the Nobel committee every year," says Jean-Marie Dubois, who studies complex metallic alloys at the University of Nancy, France.

It still isn’t clear how atoms assemble into quasicrystal structures, and the discovery has so far found few real-world applications. But the quasicrystals do have unusual and potentially useful physical properties. Although many quasicrystals are metallic alloys, they do not behave like metals: thanks to the way their electrons are confined, they are poor at conducting heat and electricity, and have non-stick surfaces, so they might be useful in low-friction coatings for frying pans. They are also very hard, and can be used to improve the strength of materials such as steel. But it is not clear that materials incorporating quasicrystals will be more useful than others currently on the market, says Ronan McGrath, a surface scientist at the University of Liverpool, UK.

Instead, Shechtman’s key contribution to chemistry was in opening scientists’ eyes to the possibility of new forms of matter. "The discovery of quasicrystals has taught us humility," writes Sven Lidin, an inorganic chemist at Stockholm University and a member of the Nobel Committee for Chemistry.

Fearful symmetry

quasicrystalThis atomic model of a silver-aluminium quasicrystal shows its mosaic pattern.Ames Laboratory

Thirty years ago, scientists thought that all crystalline materials were composed of atoms packed into regularly repeating three-dimensional lattices, similar to the hexagonal honeycomb of a beehive. This definition dictated that the basic repeating units could possess only particular symmetries: they could be rotated by one-half, one-quarter or one-sixth of a full circle and still look the same, but they could not possess pentagonal symmetry.

On 8 April 1982, Shechtman, who was on sabbatical at the US National Bureau of Standards (now the National Institute of Standards and Technology; NIST) in Gaithersburg, Maryland, found that an artificial alloy of aluminium and manganese disobeyed the rules.

When he shot electrons through the material, they created a regular diffraction pattern, proving that the material’s atomic structure consisted of orderly repeating elements. But that pattern showed a forbidden pentagonal symmetry — it could be rotated by both one-tenth and one-fifth of a full circle and would still look the same. In his laboratory notebook for that day, Shechtman wrote: "10 Fold???"

"There can be no such creature," he is reported to have said. Others did their best to persuade him that his discovery was wrong. "I told everyone who was ready to listen that I had a material with pentagonal symmetry. People just laughed at me," Shechtman told Haaretz magazine in a profile earlier this year. He was asked to leave his research group, he says.

But Shechtman got his findings published in November 1984 in Physical Review Letters, with the help of Ilan Blech, a materials scientist at Technion, John Cahn, a physicist at NIST, and Denis Gratias, a crystallographer then at the Centre for Metallurgic Chemistry in Vitry, France. "All I did was present the wonderful work that he had done in a compelling way," Cahn says.

When the paper did come out, recalls Elser, "everybody was incredulous. This was what the textbooks had told them wasn’t possible." Researchers around the world rushed to confirm the findings. Like Shechtman, they melted alloys of aluminium and manganese and put them onto a cold surface. The same diffraction pattern emerged.

"Given the relative simplicity of making these materials, it’s certain that the five-fold patterns had been seen by numerous scientists before Shechtman, who dismissed them because they didn’t fit the rigid rules of crystallography," says Elser.

Indeed, such ‘aperiodic’ five-fold structures had been described by mathematicians many decades before — most famously by British mathematician Roger Penrose. Related complex designs are found in Islamic art and architecture.

"Breaking the symmetry laws that we as crystallographers are educated on was difficult to accept," says Ada Yonath, a crystallographer based at the Weizmann Institute of Science in Rehovot, Israel, who won the Nobel Prize in Chemistry in 2009 for her work on the structure of the ribosome. "Though [Shechtman] is such a nice man I would work with him even if I disagreed with him."

  • References
    1. Shechtman, D. , Blech, I. , Gratias, D. & Cahn, J. W. Phys. Rev. Lett. 53, 1951-1953 (1984).
    2. Bindi, L. , Steinhardt, P. J. , Yao, N. & Lu, P. J . Science 324, 1306-1309 (2009).
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