New description of structural disorder in silica glass

Structural changes in cristobalite and silica glass and melt are investigated at high temperatures by molecular dynamics simulations. The calculated interaction energies are analyzed employing a new method called ‘atomistic energy distribution analysis’. Each pair-interaction energy is divided into equal halves which are allocated to each atom. Therefore, each atom has the summed-up value (‘atomistic potential energy’) of half the pair-interaction energies. First, an analysis of atomistic energy distribution functions show a correspondence with structural changes such as α–β phase transition, cristobalite melting and glass transition of SiO2, in harmony with the results obtained in our preceding study. Moreover, this study demonstrates the different roles of oxygen and silicon in terms of structural changes. Finally, newly defined order parameters offer the possibility of distinguishing structures resulting from different thermal histories through introduction of higher moments.