New description of structural disorder in silica glass. II. Application of atomistic energy distribution analysis to pressure effects

Molecular dynamics (MD) simulations have been made to study changes in density, oxygen coordination number and bond exchange during compression and decompression of quartz, cristobalite and silica glass. The interaction energies calculated by MD are analyzed in terms of ‘atomistic energy distribution (AED) with which pair-interaction energies are divided into equal halves allocated to each atom. Therefore, each atom has the summed-up value (‘atomistic potential energy’) of half the pair-interaction energies. The calculated results show different patterns and profiles in first and second moments of AED in the three silica systems, which are used to interpret pressure-induced amorphization of quartz, crystal-crystal transition in cristobalite and densification in silica glass. Making use of a previous AED analysis of thermal effects in silica glass [J. Non-Cryst. Solids. 355 (2009) 694], we finally compare and ascertain structural transformations that are due to either thermal or mechanical effects.