The Mystery of How Quasicrystals Form
The original version of This story appeared in Quanta magazine.
Since their discovery in 1982, exotic materials known under the name of quasicrystats have joined physicists and chemists. Their atoms are organized in pentagonous chains, decagons and other forms to form patterns that never repeat themselves. These models seem to challenge physical laws and intuition. How can atoms “know” how to form elaborate arrangements of non-repetition without an advanced understanding of mathematics?
“The quasi-cristals are one of those things that as a scientist of the materials, when you learn them for the first time, you say to yourself:” It’s crazy “,” said Wenhao Sun, scientist at the University of Michigan.
Recently, however, a wave of results took off some of their secrets. In a study, the sun and the collaborators have adapted a method to study the crystals in order to determine that at least some quasi -cristals are thermodynamically stable – their atoms will not be established in a lower energy arrangement. This observation helps to explain how and why the quasi-cristals are formed. A second study gave a new way of quasi-cristals engineering and to observe them in the training process. And a third research group recorded previously unknown properties of these unusual materials.
Historically, quasi-cristals have been difficult to create and characterize.
“There is no doubt that they have interesting properties,” said Sharon Glotzer, a computer physicist who is also based at the University of Michigan but who was not involved in this work. “But being able to do them in bulk, to make them evolve, at the industrial level -[that] Did not feel possible, but I think it will start to show us how to do it in a reproducible way. “”
Symmetries `prohibited ”
Almost a decade before the Israeli physicist Dan Shechtman discovered the first examples of quasicristal in the laboratory, the British mathematical physicist Roger Penrose thought that the “quasipperiodires” – the time protectors that would manifest themselves in these materials.
Penrose has developed sets of tiles that could cover an infinite plan without spaces or overlaps, in models that cannot and cannot repeat. Unlike tessellations made of triangles, rectangles and hexagons – on two, three, four or six axes symmetrical forms, and what a tile space in periodic models – Penrose pavages have a quintuple “prohibited” symmetry. The tiles form pentagonal arrangements, but the pentagons cannot adapt perfectly side by side to tile the plane. Thus, while the tiles align along five axes and endless pints, different sections of the pattern are only similar; The exact repetition is impossible. The quasiperiodic pavages of penrose made the cover of American scientist In 1977, five years before spending pure mathematics in the real world.
