• Physics 15, s86
The quirky temperature dependence of liquid silica’s viscosity comes from the liquid equal of crystal defects, in response to new simulations.
As a glass-forming liquid cools, the jostling of its particles slows, and the fabric turns into extra viscous. In some liquids, the viscosity will increase easily because the temperature decreases. In others, together with water and a few metallic liquids, the viscosity-temperature habits is extra advanced. The supply of this complexity, which includes an initially massive viscosity rise adopted by a way more gradual change, stays unclear. Now, Zheng Yu of the College of Wisconsin-Madison and his colleagues predict that the temperature dependence of silica’s viscosity is linked to thermally activated crystal-like defects that type within the liquid because it cools . The discovering may result in extra exact management of liquid silica in glass fabrication.
For his or her research, Yu and his colleagues used machine-learning-based simulations to look at liquid silica’s temperature-dependent circulate habits. Their simulations assign to every of the liquid’s silicon atoms a likelihood that it’ll change place, or “hop,” relative to its neighbors. From the hopping chances, the mannequin then estimates what number of atoms circulate by way of the liquid at a given temperature.
The simulations reveal that liquid silica’s advanced viscosity-temperature habits arises from a change within the likelihood that the atoms hop. Hopping is promoted by defects within the liquid, analogous to level defects in a crystal. The variety of these defects drops rapidly as temperature decreases, resulting in a steep drop within the probability that an atom hops and to a speedy rise within the liquid’s viscosity. Beneath a sure temperature, the defects fully disappear. The probability of the atoms hopping then follows a gradual lower, and the viscosity enhance switches to a gradual rise.
Rachel Berkowitz is a Corresponding Editor for Physics Journal based mostly in Vancouver, Canada.
- Z. Yu et al., “Understanding the fragile-to-strong transition in silica from microscopic dynamics,” Phys. Rev. Lett. 129, 018003 (2022).