Researchers at the Institute of Industrial Sciences at the University of Tokyo used calculations of molecular dynamics to simulate the ability of metal mixtures to form glass. They show that even small changes in composition can cause a material to assume a crystalline and glassy state upon cooling. This work can lead to a universal theory of glass formation and cheaper, more elastic electroconductive glass.
If you have important guests coming to dinner, you can set the table with expensive “glass” glasses. Scientists, however, are two very different situations that glass and glass can actually create when a liquid cools. Crystal has defined an indefinitely repeating three-dimensional lattice structure, while glass is an amorphous solid with no long-range ordering. Current theories of glass formation cannot determine exactly which metal mixtures will be “glazed” to form glass and which will crystallize. A better understanding of glass formation would be very helpful when designing new recipes for mechanically hard and electrically conductive materials.
Now, researchers at the University of Tokyo have used computer simulations of three prototypical metal systems to study the process of glass formation. “We found that the ability of a multi-component system to form a crystal, compared to the glass, can interrupt small changes in composition,” says first author Yuan-Chao Hu.
Simply put, the creation of glass is a consequence of the material preventing crystallization when cooled. This locks the atoms in a “frozen” state before they are arranged in an energy reduction model. Simulations have shown that the critical factor that determines the rate of crystallization is the energy of the liquid-crystal interface.
Researchers have also found that changes in the elemental composition can lead to local atomic ordering, frustrating the crystallization process with arrangements that do not match the usual shape of the crystal. Specifically, these structures can prevent small crystals from acting as “seeds” with nuclear growth in the ordered regions of the sample. Compared to previous explanations, the scientists determined that the potential chemical difference between the liquid phase and the crystals has only a small effect on the formation of glass.
“This work represents a major step forward in understanding the basic physical mechanism of glazing,” says lead author Hajime Tanaka. “The results of this project may help glass manufacturers to design new multi-component systems with certain properties, such as strength, hardness and electroconductivity.”
Reference: “Physical origin of the formation of glass from multicomponent systems” December 11, 2020, Advances in science.
(Sci. Adv. 2020; 6: eabd2928)