Domain structure and oxygen-pockets in the silica melt under pressure

We have investigated firstly domain structure and oxygen-pockets for silica melt. The result shows that the structure comprises separate domains and boundaries between them. The domains occupy dense regions, while the boundaries between domains occupy loose regions. We found a number of Oxy bonded to three Si types. The structure undergoes through one- and two-domain pressure regions. A number of oxygen-pockets are found, and their volume reaches up to 1100 Å3. The densification is realized by decrease in Voronoi volume and transformations of Si4→Si5, Si5→Si6 and O2→O3. Further analysis indicates that at ambient pressure the exchange of coordinated O between basic units happens non-uniformly through the network structure, which causes the dynamics heterogeneity.