The diffusion of Si and O ions in simulated liquid SiO2 at high pressures (or high densities) was studied using a model which contained 3000 ions with periodic boundary conditions and pair-wise interatomic potentials which had 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 5.35g/cm3 were heated from 350 to 7000K, via molecular dynamics simulation, and the diffusion constant was calculated from above the melting point to 7000K. The calculations showed that the temperature dependence of the diffusion constant of components in the system exhibited an Arrhenius behavior at relatively low temperatures above the melting point and obeyed a power-law, D  (T-Tc)γ, at higher temperatures. Dynamic heterogeneities were observed under high pressures.

Diffusion and Dynamical Heterogeneity in Simulated Liquid SiO2 under High Pressure. V.V.Hoang, H.Zung, N.T.Hai: Journal of Physics - Condensed Matter, 2007, 19[11], 116104 (14pp)