Thermodynamic pathways of silica glass densification by molecular dynamics simulations

Aram Yedigaryan, Elena Kachan, Jean-Philippe Colombier

Abstract: The understanding of the structural evolution of silica glass under various thermodynamic conditions contributes to the optimization of densification processes of silica in laser-writing applications. In this study, we thus explore thermodynamic pathways for the densification of silica glass using molecular dynamics (MD) simulations. First pathway involves a standard pressurization simulation where the system is initialized in a crystalline state. A silica polymorph undergoes a melt-quench process, transitioning into an amorphous phase with a density lower than the one of the crystal. It is then followed by a pressure increase to densify the material and gradual relaxation into a stable, densified amorphous phase. Another method for densification follows an isochoric pathway, where the volume of the system is kept constant during the initial amorphization process. After quenching and relaxing the system from high temperatures, the volume constraint is removed, and the system is allowed to relax under ambient pressure. The procedure is performed starting with two different crystalline polymorphs, \(\alpha\)-quartz and stishovite, to study the effect of the initial configuration on the final result. The MD simulations demonstrate that pressure control of silica glass yields up to 8% densification, while isochoric amorphization of \(\alpha\)-quartz and stishovite produces glasses that are 7% and 11% denser than silica glass, respectively.

External IDs:doi:10.1007/s00339-025-08702-9