Despite all that we know about the properties of the materials we call glass, there is so much more that is still a mystery.
When we think of the physical properties of glass it calls to mind the obvious reasons it is so common and so useful. It is a hard, clear, non-reactive material. It is perfect for food storage. It has optical qualities that make it a great choice for windshields, window panes, eyewear, and telescopes. It responds well to gradations in temperature and absorbs heat well. Think glass cookware – it even has insulating qualities that make it resistant to electric current.
But when science defines the properties of glasses, it refers to their atomic groupings and states of matter, as in gas, liquid, or solid. And for scientists, many age-old questions remain about the behavior of glass as it transitions from liquid to solid.
Typically, molecules in a liquid state are attracted to each other but don’t “cling.” Instead, they dance around in random motion allowing them to flow. When a typical liquid hardens, the molecules form crystals that are bonded to each other in a precisely organized and static pattern, thus achieving rigidity. But glass molecules do not form neatly patterned crystals when cooled; instead, the atoms are “set” in a disordered manner before having the opportunity to crystallize into a solid. So glass maintains both a solid and liquid state simultaneously. It is “amorphous” rather than crystalline.
The National Science Foundation (NSF) has recently awarded funding to researchers from a number of disciplines to delve into just a few of the bewildering properties of glasses from their varying professional perspectives. There is room for researchers from mathematics, physics, materials science, chemistry, medicine, and even the arts, whose specific application would benefit from a better understanding of why glasses dance to the beat of a different drum than other materials.
A team from NYU’s Center for Soft Matter Research undertook the challenge of uncovering just what it is about the disordered arrangement of molecules that determines whether the glass will exist in a liquid or solid state. Why does it not behave according to the usual rules of matter? What is going on at the microscopic level during the transition?
But finding out what goes on in the internal structure of glass is not so easy due to the disorganized arrangement of molecules, and the constituent particles can be “as small as a billionth of a meter in size.” These researchers worked with “colloidal suspensions” that become solid when the density increases to a certain threshold. They theorize that “crowding” plays a part in restricting “flow” of the particles because they are “contained” by the framing of their neighbor particles. They offer their findings in a paper published in “Proceedings of the National Academy of Sciences.”
Another grant was afforded to a team from Penn State University and Argonne National Laboratory in Illinois to work with “Coulomb” glass so as to develop a mathematical approach to investigating this mystery. “Our goal,” says Leonid Berlyand of Penn State, “was to find a simple approach that would reduce the computational complexity caused by frustration allowing us to approximate the ground state of glassy systems.”
“Frustration” is the technical term used to describe the competition taking place between the particles that disallow some of them from finding a grounded resting place. Because of this frustration, there is too much computational complexity that allows for a “multitude of energetically equal possibilities.” So the researchers adopted the well-understood and universal Ginzburg-Landau equation, which is a means of establishing a “unified language” to approach an understanding of “instabilities” in dynamic structures.
The results allowed the researchers to approximate the “ground state of glassy systems” to discover that “the electrons in a two-dimensional Coulomb glass interact with each other in the same way as the vortices of magnetic force that form in superconductors interact.”
This approximation of the ground state of Coulomb glass provides a platform for other research to take place. According to Argonne Distinguished Fellow, Valerii Vinokur, “Our approximation is similar to how tourists reach the top of Mount Fuji. No one starts at the bottom anymore. You start at base camps half-way up the mountain that make the trip shorter and easier.”
I love it when scientists get metaphorical. And how Zen is it when one finds deep satisfaction not in an end game, but in providing a platform for progress for those scientists and researchers who come behind? Scientists may be portrayed as boring nerds with limited life experiences, but look more closely, and you might recognize the poet who sees the world with a sense of wonder.
Though most of us see glass as a common and simple material, we should be glad that others appreciate its mysterious behavior and fixate on the question of why.
