Equation of state of SiO2 glass at high pressure investigated with AIMD simulation

The equation of state (EOS) for silica glass is crucial for understanding the structure, properties, and modeling of silicate materials under extreme conditions, making it of significant importance in condensed matter physics, materials science, and geoscience. While accurate density measurement of non-crystalline materials (NCM) under high pressure remains a major challenge, ab initio molecular dynamics (AIMD) simulations can reveal atomic structures and provide insights into the equation of state (EOS) between volume and external pressure. In this paper, we present the results of an EOS study of SiO₂ glass, based on two relatively large AIMD simulation boxes, i.e. 81 SiO₂ units (243 atoms) and 192 SiO₂ units (576 atoms), with periodic boundary conditions using high accuracy algorithms in AIMD simulations. The obtained EOS of SiO₂ glass undergoes significant changes at compression volume ratios V/V₀ of 0.46 and 0.59, forming an intermediate state within this range resembling that observed in GeO2 glass under high pressure. The pressure-induced tetrahedral to octahedral transition of network-forming SiO₂ glass can be addressed by AIMD method.