Diffusion and dynamical heterogeneity in simulated liquid SiO2 under high pressure

Diffusion of Si and O ions in simulated liquid SiO2 under high pressure (or high density) have been studied in a model containing 3000 ions under periodic boundary conditions with pairwise interatomic potentials which have a weak electrostatic interaction and Morse-type short-range interaction. In order to observe diffusion in the liquid state, amorphous models at fixed densities of 2.20, 4.30 and 5.35 g cm-3 have been heated up from 350 to 7000 K via molecular dynamics (MD) simulation and the diffusion constant has been calculated at temperatures ranging from above the melting point to 7000 K. Calculations show that the temperature dependence of the diffusion constant D of components in the system shows an Arrhenius law at relatively low temperatures above the melting point and shows a power law, D ∝(T-TC)γ, at higher temperatures. Dynamical heterogeneities under high pressure have been observed and discussed