Effect of pressure quenching on the structures and properties of borosilicate glasses: Insights from molecular dynamics simulations

Abstract

Combining thermal and pressure effect represents a novel approach to modify glass properties. However, the microscopic structural origin of these property modifications is complex and far from fully understood, especially in multicomponent glasses with mixed glass formers. In this paper, we have utilized classical molecular dynamics simulations with a set of composition dependent potentials to investigate pressure-quenching effect on sodium borosilicate glasses. Processes including hot compression, cold compression and subsequent annealing on the structures and properties are investigated and compared. It was found that applying pressure up to 10 GPa at the glass transition temperature led to permanent densifications and a dramatic increase of elastic moduli by 90%, while thermal annealing reversed the increase and applying pressure at ambient temperture did not increase the modulus. The main structural change of the hot compressed sample is the increase of four-fold coordinated boron while silicon remains four-fold coordinated. The sodium environment shows an increase of coordination number and a decrease of NaO and NaNa bond distances. Medium range structure is also changed with an increase of 8-membered rings. These results provide atomistic insights of the pressure quench effect on borosilicate glasses.