Polyamorphism and Two State Model in Liquid GeO$_{2}$ under Compression: Insight from Visualization of Molecular Dynamics Data

Abstract

The polyamorphism and two-state model based on the coordination number distribution in liquid GeO$_{2}$ at 3200~K and in a wide pressure range are investigated by molecular dynamics simulation. Results show that the structure of liquid GeO$_{2}$ mainly consists of GeO$_{x}$ coordination units $(x=4,5,6)$ and OGe$_{y}$ linkages $(y=2, 3)$. The distribution of OGe$_{y}$ linkages in network structure is not uniform but tends to form clusters of OGe$_{y}$. The cluster of OGe$_{2}$ will form low-density phase region, conversely the cluster of OGe$_{3}$ will form high-density phase region. In other word, under compression, in the liquid GeO$_{2}$ coexist two states: low-density and high-density. The size of phase regions significantly depends on compression.