3 min readHere’s what you’ll learn when you read this story:
- Since 1948, scientists have wondered: If you could cool a glass over an extremely long period of time, would it eventually form an amorphous structure that behaves exactly like a crystalline lattice—a state known as ideal glass?
- Now, a new study has computationally constructed such a glass in two dimensions by forming a honeycomb-like structure (with the lattice removed) and allowing glass molecules to resize.
- The resulting structure behaved perfectly like a crystal, but held an amorphous structure like glass—possibly shining a light on how to more effectively form other materials.
Although we may take it for granted in our everyday lives (for the past 5,000 years or so), glass is a bit of a scientific conundrum. While glass is most definitely a solid, it’s made of disordered molecules like a liquid. By some descriptions, that makes a glass a type of “liquid in suspended animation” because its liquid-like molecules don’t flow, and they also don’t crystalize like a solid.
But in 1948, American chemist Walter Kauzmann proposed a strange question: Could glass, if cooled slowly enough, form a perfect arrangement of the densest possible amount of molecules, or an ideal-glass state? Kauzmann realized that the slower you cool down a liquid, the more time the molecules would have to rearrange. So, once the liquid reached the same level of entropy as typically exists when a crystal forms, the glass might form a perfect order where each molecule affects the position of the other. Unfortunately, cooling glass to this state would require essentially an infinite amount of time, and the overall paradoxical nature of “ideal glass” eventually led Kauzmann to dismiss the idea.
However, in a new study published in the journal Physical Review Letters, a team of researchers—hailing from universities across the U.S. and led by Eric Corwin, a physicist from the University of Oregon (UO)—computationally demonstrated that such an “ideal glass” state is possible in two dimensions.
“If you look at glass at a molecular level, you would see that the molecules are arranged amorphously. They’re kind of random. They’re all pushed up against one another, but there’s no structure,” Corwin, senior author of the study, said in a press statement. “How do you get stability, mechanical stability, in a system that is totally amorphous, that looks like a liquid?”
To answer that question, Corwin and his team used UO’s high-performance computer to computationally construct 2D disks clustered together (sort of like cells in a honeycomb) and then preserve that structure while removing the crystalline lattice. They then allowed the glass particles to resize as they packed, and the resulting structure appeared amorphous like glass, but exhibited all known crystalline properties (such as how a material responds to pressure, bending, and melting).
“We think that we’ve hit upon a resolution, by showing that such a state is not a paradox at all; indeed we can construct it,” Corwin told Phys.org. “We’ve shown that one can’t hope to achieve these structures just by waiting, but that they nevertheless exist. The fact that a structure with no spatial ordering (i.e. an amorphous structure) can still be highly ordered in a more abstract sense (i.e. zero configurational entropy) is an enormous surprise.”
While Corwin and his team still need to expand their research into three dimensions, understanding that “ideal glass” can be constructed at all could improve manufacturing techniques for other materials, including metallic glass (metallic structures with disordered configurations like glass).
“If we could develop a much better understanding of the glass transition and understand what makes an alloy better or worse at forming a metallic glass, we could design alloys that you could cool much more slowly,” Corwin said in a press statement. “It would be revolutionary.”
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Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.