Static and Dynamic Heterogeneities in Supercooled SiO2

Abstract

Static and Dynamic heterogeneities in supercooled SiO2 have been investigated in the models containing 3000 particles obtained by cooling from the melt with the pair interatomic potentials, which have the Morse type part for the short-range interaction. The evolution of structure of the system upon cooling was presented and analyzed in details through the changes in the partial radial distribution functions (PRDFs), coordination number distributions, bond-angle distributions and structural defects. Calculation presented that the temperature dependence of diffusion constant D of components in the system shows an Arrhenius law at low temperatures and it shows a power law, γ ) ( C T T D − ∝ , at high temperatures. The critical temperature Tc is equal to 4200 K and the exponent γ is close to 0.50. In order to study the dynamical heterogeneities in the system, we evaluated the non- Gaussian parameter for the self-part of the van Hove correlation function and luster-size distributions of most mobile or immobile particles in the model. We compared the PRDFs for the 10% most mobile or immobile particles with the corresponding mean ones. We have found that the most mobile and immobile particles form clusters and mean cluster size grows with decreasing temperature.