Inelastic relaxation in silica via reactive molecular dynamics

Abstract

AbstractSilica glass exhibits rate‐dependent and irreversible processes during deformation and failure, resulting in inelastic effects. To explore this phenomena, molecular dynamics simulations of structural relaxation surrounding a crack tip in silica glass were performed at four different temperatures (100, 300, 600, 900 K) using a reactive force field. Per‐atom stresses were found to relax during the simulation, with the highest stress relaxation occurring at 900 K. Stress relaxation was radially dependent relative to the crack tip, with stress dissipation occurring primarily within a 25–30 Å inelastic region. Within 10 Å of the crack tip, the defect concentration decreased from 0.18 to 0.09 #/nm2 during inelastic relaxation at 900 K. Conversely, the defect concentration 20 Å from the crack tip increased from 0.105 to 0.118 #/nm2 at 300 K, and from 0.113 to 0.126 #/nm2 at 600 K, which formed a defect‐enriched region ahead of the crack tip. The difference in defect concentrations suggests the possibility of a stress mediated defect migration mechanism, where defects move away from the crack tip during inelastic relaxation. Additionally, defect speciation indicated that undercoordinated silica defects, such as non‐bridging oxygen, were removed through the formation of higher coordination defects during relaxation. Overall, stress relaxation causes changes in the defect concentration profile near the crack tip, which has the potential to alter the properties of silica glass in the inelastic region during relaxation.