A team of researchers working at the university of Notre Dame has discovered a whole new group of quasicrystals. In their paper published in the journal Nature, the team describes how they accidently created a new kind of quasicrystal as part of a series of experiments designed to learn more about electron distribution in ferrocenecarboxylic acids.
Quasicrystals are groups of molecules bonded together in structures that resemble crystals in that they are organized, but unlike crystals, the structures are not nearly as uniform. In fact, they are quite the opposite—though they are locally symmetric, they lack any sort of long distance periodicity. Because of their chaotic nature, quasicrystals tend to feel slippery to the touch, which is why they have been used to coat the surface of non-stick frying pans. The first quasicrystal was made, also by accident, in 1982, by Daniel Shechtman (who later won a Nobel prize for his work). Since then many more of them have been made in various labs, (one was even found to exist in a meteorite) though most of them have had one thing in common, they were all formed from two or three metal alloys.
In this latest discovery, the quasicrystals self-formed after the researchers placed a layer of iron containing molecules of ferrocenecarboxylic acid on top of a gold surface. The team was expecting to see a linear group of stable molecules pairing up as dimers, but instead were surprised to find that they had formed into five sided rosettes—it was the rosettes that pushed other molecules into bonding forming crystalline shapes, resulting in the formation of 2D quasicrystals that took the form of several different shapes: stars, boats, pentagons, rhombi, etc., all repeated in haphazard fashion.
In studying the quasicrystals using scanning tunnelling microscopy, the researchers found that they were held together by weak hydrogen bonds rather that the strong ionic bonds found in other such molecules. Weak hydrogen bonds are generally more common in organic molecules that exhibit complex structures.
In their paper, the researchers suggest their discovery might lead to the creation or discovery of many other similar types of quasicrystals, though it's still not clear to what use they might be put.
