Molecular dynamics study of pressure enhancement of ion mobilities in liquid silica.

Abstract

Melts of many silicates are known to have an anomalous transport property in that the diffusivity of oxygen atoms drastically increases with pressure. Here we propose a mechanism for the anomalous diffusion process in liquid silica and silicates on the basis of molecular dynamics (MD) results for pressure-induced structural transformations in crystalline silica. The model is successfully tested with a MD simulation for liquid silica with an interatomic potential based on a first-principles calculation. A close relation between the diffusivity of oxygen atoms in molten state and the relative stability of polymorphs of silica is clarified.