First-principles study of crystalline silica

Abstract

We have investigated the structural properties of five difFerent crystalline forms of Si02 using a firstprinciples approach. An ultrasoft Vanderbilt pseudopotential is generated for oxygen which enables us to use a small plane-wave cutofF of 25 Ry. The relative stability, the equation of state, and pressuredependent structural parameters of all five polymorphs have been calculated and found to be in very good agreement with available experimental results.

Silica molecular dynamic force fields—A practical assessment

“…An effort to decouple the activation energy for diffusion from melting temperatures by devising force fields for which the activation energy for bond breaking shown in Fig. 1 was increased while maintaining a reasonable cohesive enthalpy between 20 and 30 eV 42 were not successful. Our results also suggest that a "strong" glass former defined as one with little change in heat capacity at the glass transition is one in which hopping from one minima to another results in no significant change in potential energy, for example topological changes in the silica ring network by exchanging corner sharing tetrahedral connections.…”

Morse Stretch Potential Charge Equilibrium Force Field for Ceramics: Application to the Quartz-Stishovite Phase Transition and to Silica Glass

“…[ S0031-9007(99) In principle, the phase transitions in minerals and ceramics can be predicted from first principles quantum mechanics (QM), and significant progress is being made along this line [1][2][3]. However, most QM studies have considered only static conditions since dynamical QM simulations are usually not practical for long times (at least nanoseconds) and large system sizes of interest for ceramics.…”

“…This MS-Q potential is applied herein to SiO 2 , where we find that it describes well the fourfold coordinated and sixfold coordinated systems (such as quartz and stishovite), silica glass, and the pressure-induced phase transition from quartz to stishovite. In principle, the phase transitions in minerals and ceramics can be predicted from first principles quantum mechanics (QM), and significant progress is being made along this line [1][2][3]. However, most QM studies have considered only static conditions since dynamical QM simulations are usually not practical for long times (at least nanoseconds) and large system sizes of interest for ceramics.…”

“…We then cooled the system slowly (4 ps per 100 K) using constant volume, constant temperature ͑NVT ͒ dynamics until 1000 K. At 1000 K, we switched to NPT dynamics and continued cooling at the same rate. Finally, we performed 30 ps NPT dynamics at 300 K, leading to a final density of 2.32 g͞cm 3 . In a second simulation we cooled the systems more slowly (8 ps per 100 K) and found the final density, 2.33 g͞cm 3 .…”

“…Finally, we performed 30 ps NPT dynamics at 300 K, leading to a final density of 2.32 g͞cm 3 . In a second simulation we cooled the systems more slowly (8 ps per 100 K) and found the final density, 2.33 g͞cm 3 . This indicates that slower cooling is unlikely to change the density.…”