Temperature-induced densification of compressed SiO2glass: A molecular dynamics study

Annealing to several hundred Kelvin has been recently shown to induce densification in compressed SiO2 glass. By means of an ab-initio parameterised interatomic potential for SiO2 and molecular dynamic simulations, we studied the structural properties of compressed glass by cold compression at room temperature and by quenching the liquid at selected pressures. The noticeable differences found below 10 GPa between the two results are interpreted in the context of the experimentally reported temperature-induced densification and of the speculated occurrence of a first-order transition between two distinct polyamorphs. Calculated X-ray and neutron structure factors agree well with available experiments, and indicate that structural differences between annealed and cold-compressed forms take place at distances of 3.5–4 A. In contrast, short-range order (atomic coordination, bond length and angular distribution functions) is identical in the two forms of silica glass.