The Structural Phase Transition, Degree of Polymerization and Dynamics Characteristics of Liquid Magnesium Silicate: A Molecular Dynamics Simulation

Abstract

In this paper, the structural phase transitions, degree of polymerization, and dynamics characteristics in liquid magnesium silicate (Mg2SiO4) under pressure have been studied using molecular dynamics (MD) simulation. The results indicate that the structure of Mg2SiO4 liquid includes MgOy (y = 3, 4,…8) basic units distributed in the Si-O structure network that powerfully depend on pressure. In the range 28-32 GPa, the Si-O structure network causes structural transformation from SiO4 to SiO6 via SiO5 units. Mg-O and Si-O subnets tend to form clusters with structural heterogeneity. The degree of polymerization is considered via characteristics of OT2 (T is Si or Mg), triclusters, tetraclusters bonds, and the cluster of MgOy-MgOy, SiOx-SiOx and MgOy-SiOx links. We indicated that the degree of polymerisation significantly increases with the increasing pressure. The dynamic in Mg2SiO4 liquid has been investigated through the self-diffusion, low and fast atoms. The evidence about the fast diffusion of Mg atoms in a low-pressure range is also indicated in here.