Structural and topological changes in silica glass at pressure

Abstract

The effects of high pressures on the structure of silica glass have been elucidated using high-energy x-ray diffraction up to 43.5 GPa. A decrease in the first two peak positions in the real-space pair-distribution functions up to 15 GPa indicates an initial shrinkage of the tetrahedral units. Above this threshold pressure the Si-O bond peak shape becomes asymmetric and the average Si-O bond length and coordination number both increase linearly with pressure. Also, strained geometries in the O-O correlations lead a pronounced topological rearrangement of the second and third nearest neighbors.