by Kenneth Chang | NYTimes.com | October 5, 2011
The scientist Daniel Shechtman, right, during a news conference in Haifa, Israel, on Wednesday after winning the Nobel Prize in chemistry for his discovery of quasicrystals. Photo: Ariel Schalit/Associated Press
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.