Mechanical strength and coordination defects in compressed silica glass: Molecular dynamics simulations

Abstract

Contrary to ordinary solids, which are normally known to harden by compression, the compressibility of SiO 2 ͑silica͒ glass has a maximum at about 2-4 GPa and its mechanical strength shows a minimum around 10 GPa. At this pressure, the compression of silica glass undergoes a change from purely elastic to plastic, and samples recovered from above 10 GPa are found to be permanently densified. Using an improved, ab initio parametrized interatomic potential for SiO 2 we provide here a unified picture of the compression mechanisms based on the pressure-induced appearance of unquenchable fivefold defects. By means of molecular-dynamic simulations we find them to be responsible for the reduction of the mechanical strength and for permanent densification. We also find that the compressibility maximum does not require changes of the tetrahedral network topology.

Elastic anomalous behavior of silica glass under high-pressure: In-situ Raman study

“…According to Trachenko and Dove and Walker et al works [16][17][18], maximum compressibility arises in this range of pressure because there is a low-energy buckling of the network through weak rotations of SiO 4 tetrahedra. Huang and Kieffer and Haung et al [14][15] and Liang et al [13] suggest a gradual and localized polyamorphic transition similar to those which underlie the b-to-a transition in cristobalite.…”

“…However, the density increases. Several recent molecular-dynamics simulations under various pressures [13][14][15][16][17][18] have tried to explain what happens between 0 and 2 GPa, namely in the bulk modulus anomalous behavior domain. According to Trachenko and Dove and Walker et al works [16][17][18], maximum compressibility arises in this range of pressure because there is a low-energy buckling of the network through weak rotations of SiO 4 tetrahedra.…”

“…As yet, all physical measurements give information on the macroscopic level during compression but at the atomic scale, only simulations tried to interpret this transformation [13][14][15][16][17][18].…”

An Ab Initio Molecular Dynamics Study of Bioactive Phosphate Glasses

“…Since it is commonly difficult for MD simulations to reproduce both experimental density and pressure of glasses, [34,[36][37][38][39][40][41][42] in this study we have decided to reproduce the experimental density. The accumulated average pressure of our models is around 2 GPa, but, according to previous MD studies of silica and phosphosilicate glasses, [43,44] the structural and dynamical properties of glasses at this level of pressure do not significantly change with respect to 1 atm.…”

The effect of high-pressure densification on ballistic-penetration resistance of a soda-lime glass

“…Since that time, major advances in computer technology and the introduction of high-fidelity quantum mechanics-based force fields (inter-atomic potentials) have allowed for more accurate computational modelling of glass elastic constants, strength, chemical and thermal diffusivities, surface energies, etc. Of interest to this study, a great number of researchers have investigated, using molecular modelling techniques, the propensity of various types of glass (of different chemistries and microstructures) to undergo irreversible (permanent) densification when subjected to high hydrostatic pressures on the order of 10 GPa [6][7][8]. The emphasis in these investigations was placed on elucidating the main atomiclevel mechanisms and processes (e.g.…”