HIGH-PRESSURE DENSIFICATION OF SILICA GLASS - A MOLECULAR-DYNAMICS SIMULATION

We have performed a molecular-dynamics simulation for a sample of amor phous SiO2 subject to a compression-decompression process at ambient t emperature, using a recently proposed two-body potential model. For mo derate compression the simulated glass maintains the ideal tetrahedral coordination and displays reversible elastic behavior. For compressio ns beyond 6 GPa, the glass becomes anelastic and its density and avera ge atomic coordination increase irreversibly. Density, compressibility , and structure of the simulated material compare favorably with the e xperiments on both undensified and densified SiO2 glass. The stability of Si-O coordination greater than four in samples subject to high pre ssure appears to drive the densification process.