Densification of silica glass under pressure

We present the results of a simulation study of the effects of pressure on structural changes in silica glass. We observe structural relaxations in glass under pressure that involve large atomic displacements and are accompanied by breaking of the original bonds and forming of new ones. A large proportion of the new topological arrangements formed during pressurizing are preserved in structures on decompression, resulting in the irreversibility of topological changes. Substantial rebonding makes the mechanism of densification in glass essentially different from that present in transitions between crystalline silicas. We find that higher temperature promotes the degree of rebonding and densification in decompressed structure. (author)