Crystallisation of liquid silica under compression: a molecular dynamics simulation

In this study, we employ molecular dynamics simulations to develop a large model (19,998 atoms) of liquid SiO2 at 3500 K. We construct models at different pressures in the 0-100 GPa range using the Beest-Kramer-Santen (BKS) potential and periodic boundary conditions. The goal is to detail the structural transition from the polyamorphic liquid state of SiO2 to the crystalline stishovite form, which occurs between 45 and 60 GPa. We analyse the polyamorphic state of liquid SiO2 by examining the formation of SiOx clusters from 2 to 60 GPa. Beyond 60 GPa, the pair radial distribution functions (PRDFs) for Si-O, O-O and Si-Si display multiple peaks, indicating the crystalline phase. This observation is further supported by examining the bond angle distribution, the fraction of SiOx units and OSix linkages, Si-O bond lengths within SiOx units, structural visualisations and the analysis of ring statistics in the liquid SiO2 system, all of which underscore the comprehensive changes in the structure of the system.