Molecular dynamics simulation of amorphous silica under pressures

Abstract

Abstract Models of amorphous silica have been produced at 500 K, and in pressures range 0 ÷ 100 GPa by molecular dynamics simulation. Topological analysis is performed based on the basic units and transition to different a-types, where a is the Oxx and Oxy (x, y = 4, 5, 6). The simulation shows that the fraction of different types of basic units varies strongly and the mid-range structure modifies stronger than the short-range structure under pressure. In the 0 ÷ 100 GPa pressure range, structure of amorphous silica occurs the transformation from D4-to D6 domain which correspond to the intervals of 0 ÷ 5 , 5 ÷ 15 and 15 ÷ 100 GPa. We also found a number of O 456 connected with three different Si atoms. Upon compression, the structural change is accompanied with the O x x → O x y transition and two parallel processes: merging and splitting of domains which relate to the change of domain-boundary atoms.