Silica glass structure generation forab initiocalculations using small samples of amorphous silica

Abstract

Multiple small samples of amorphous silica have been generated and optimized using classical dynamics and the van Beest-Kramer-van Santen ͑BKS͒ empirical potential function. The samples were subsequently optimized and annealed using density functional theory ͑DFT͒ with both the local density and the generalized gradient approximations. A thorough analysis of the local and medium-range structure of the optimized samples obtained from the different methods was carried out. The structural characteristics obtained for the average of small systems each containing ca. 100 ions are compared for each of the different methods, and to the BKS simulation of a larger system. The differences found between the DFT and BKS simulations and the effects of volume relaxation on the structures are discussed. Fixed-volume samples are compared to neutron scattering data, with good agreement to 5 Å, the length limit of the sample sizes used here. It is shown that by creating multiple small samples, it is possible to achieve a good statistical sampling of structural features consistent with larger simulated glass systems. This study also shows that multiple small samples are necessary to capture the structural distribution of silica glass, and therefore to study more complex processes in glass, such as reactions.

Theoretical study of the insulating oxides and nitrides: SiO2, GeO2, Al2O3, Si3N4, and Ge3N4

“…Table II contains the bond lengths and bond angles of the optimized oxide polymorphs. These results can be used to identify the representation of each polymorph within the amorphous oxides 52 . The elastic constants and dielectric permittivity tensor of each crystal are tabulated in Table III and Table IV, respectively.…”

Thermochemical and Mechanical Stabilities of the Oxide Scale of ZrB2+SiC and Oxygen Transport Mechanisms

“…We have adopted the structure generation approach of Van Ginhoven, Jonsson, and Corrales, 35 which was shown to reproduce experimental pair distribution functions for pure silica. The approach requires a classical interatomic potential to perform long-time molecular dynamics (MD) simulations at the beginning, followed by further DFT optimizations.…”

First-Principles Investigation of Low EnergyE′Center Precursors in Amorphous Silica

“…Three-and five-fold Si have been reported in previous simulations [13,17]-fast cooling rates in MD simulation tend to artificially trap large numbers of these defects-however, their formation energy has not been reported. Their appearance as isolated defect pairs in our simulations with slower cooling rates and low formation energies indicate that III-Si and V-Si are likely a native defects in a-SiO 2 .…”