Scientists Discover New Class of Solids That's Neither Crystal Nor Glass: Q-Glass

There may be a new category when it comes to deciding what sort of solid you're dealing with. Scientists have discovered a new branch of solids that are neither pure glass, nor crystal nor even exotic quasicrystal. The findings could give researchers a new material to work with in the future.

The scientists first discovered the material in small, discrete patches of a rapidly cooled mixture of aluminum, iron and silicon. A type of solid alloy, the material appeared to have none of the extended ordering of atoms found in crystals. This would, in theory, make it a glass. However, the material also had a very defined composition and grew outward from "seeds"--something that glasses certainly do not do.

Crystals fill up space with atoms or molecules in specific, fairly rigid patterns. The positions of the atoms are fixed such that if you take any section of pure crystal and slide it up, down, in, out or sideways a given distance, it will fit perfectly in the new position. Glasses, in contrast, do not have symmetry. Instead, they're a random arrangement of their components, as if you'd taken a liquid and suddenly frozen everything in place without giving the atoms a chance to get in order. This is actually how metallic glasses are made.

The new material has been dubbed a "q-glass." It has neither rotational nor translational symmetry, just like a glass. However, its atomic arrangement is apparently not random; as the nodule grows, every atom still "knows" where to go. In addition, the new material has a strict chemical composition. Seen under a microscope, the q-glass can be seen to grow outward from a seed during cooling and exclude atoms that don't fit.

"It's rejecting atoms that aren't fitting into the structure, and if there's no structure, it's not going to be doing that," said Lyle Levine, one of the researchers, in a news release. "It's amazing. Everything you can think about this thing behaves like a crystal, except it isn't."

Of course, there's the possibility that this new material could just be a very strange crystal. "Frustration," in particular, could be occurring. This phenomenon happens when two or more incompatible crystal orders may start growing from the seeds and continually interfere with each other, destroying any long-range order. Yet there's also the fact that this could indeed be a new material.

"One exciting possibility is that the q-glass is the first example of a 3-dimensionally ordered configuration of atoms that possesses neither translational nor rotational symmetry," said Levine. "Such structures have been theorized by mathematicians, but never before observed in nature."

Currently, the scientists are conducting more studies on the material in hopes that they can glean more information about q-glass.

The findings are published in the journal Physical Review Letters.