Topological analysis on structure and dynamics of SiO2 liquid with the help of Si-particle and O-particle statistics

Abstract

A large model of silica liquid has been produced at temperature of 3000 K and ambient pressure by molecular dynamics (MD) simulation. We propose a topological analysis based on shell-core particles. Our result shows that the dynamics is spatially sparse due to the SiO4 ↔ SiO5 and OSi2 ↔ OSi3 transformations happen non-uniformly in the network structure. The simulation reveals Si-particles having 2 Si and O-particles containing up to 14 O. The network structure comprises clusters of particles which occupy micro-regions with pure compositions. The number of atoms in a Si-cluster varies from 2 to 7, and the O-cluster contains up to 63 atoms. We also found particles and clusters of particles which are stable for a long time. The stable particle and cluster of particles occupy micro-regions where the atoms of the same ion type are confined. The strong chemical Si–O bonds between core and shell atoms prevent those particles from breaking apart. The atoms of rigid SiO4 tetrahedrons are not uniformly distributed in the network structure, but instead they gather into domains containing the rigid Si–O subnets, stable particles and clusters of stable particles.