Simulation study of polymorphism and diffusion anomaly for SiO2 and GeO2 liquid

Abstract

We report molecular dynamic (MD) simulations of a silica and germania liquid. We show for the first time that the liquid models constructed of the BKS and Ocffner-Elliott potential are composed of D4, D5 and D6 domains. These domains of different liquids (identical chemical composition but different density) are structurally identical. The liquid densification occurs gradually with variation in the volume of the D 4, D5 and D6 domains. The void radius distributions (VRD) have been computed and they are well fitted to a Gaussian form. Both the average void radii and width of the VRD decrease with pressure. The diffusivity of Si/Ge or O depends linearly on the fraction of TOx (x = 4, 5 and 6; T is Ge or Si). The diffusion anomaly results from the very high mobility of silicon in the D5 domain compared to domains D 4 and D6. © 2009 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.