20-sided crystal, once thought impossible, found in meteorite

Once upon a time, scientists thought that quasicrystals — exotic materials with an orderly pattern that never exactly repeats itself — could not possibly exist. Then they made some in a lab in Nobel-winning research. Next, scientists thought that quasicrystals could not exist in nature. Then they found quasicrystals with the same properties as the lab-created ones in nature — specifically, in tiny fragments of a meteorite.

Now, researchers have found an entirely new, extreme type of quasicrystal with an icosahedral — 20-sided — symmetry. By contrast, most regular crystals in nature have an atomic structure with three or four sides. Paul Steinhardt, one of the physicists behind the discovery, described why this 20-sided symmetry seems almost impossible.

If you were tiling the floor of a room, Steinhardt said, you would need tiles of one of a few shapes: triangles, squares or hexagons. Anything else would leave gaps. However, if you changed the shape of the wall to curve in the right way, you could fit different shapes — akin to the the way a soccer ball has pentagonal patches that stitch together. So much like how pentagonal tiles would not work on a flat floor, a 20-sided atom can only fit together into quasicrystals.

“Nature actually beat us, made it before humans did,” said Steinhardt, who works at Princeton University. “And hopefully it’s the beginning of more.” Steinhardt and his team published a report on the new material in Scientific Reports.

Once you understand a substance — its elastic properties, slipping properties and conductivity — then you can find applications for it. So far, scientists have noticed that quasicrystals are strong, do not corrode and are more ductile than other substances. They are also very brittle. The research team has not identified specific applications of the new quasicrystals, but Steinhardt is exploring using them to channel light and make light circuits.

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