A statistical study was made of Si and O neutral defects in a silica glass model. This involved 2 complementary approaches: first-principles calculations and empirical potential molecular dynamics. It was shown that the defect formation energies and structures were distributed, and that the energy distributions were related to the local stress before defect formation. By combining defect energies calculated from first principles, and local stresses from empirical potential calculations in undefected silica, it was possible to predict the formation energy distributions in larger systems (whose size precluded the use of ab initio methods). By using the resultant predictions, it was shown that the cell-size used in the modelling contained all of the formation energy fluctuations needed to describe a real glass.

Neutral Self-Defects in a Silica Model - a First-Principles Study. L.Martin-Samos, Y.Limoge, J.P.Crocombette, G.Roma, N.Richard, E.Anglada, E.Artacho: Physical Review B, 2005, 71[1], 014116 (12pp)