Microstructural evaluation of simulated sodium silicate glasses

A molecular dynamics study of sodium trisilicate and sodium disilicate glasses has been performed in order to evaluate structural details of these systems. The total potential energy is a function of both two-body and three-body interactions in order to account for the partially covalent nature of silica bonding. The simulations reproduce the bulk structural features observed in XRD and EXAFS experiments. The simulations show that the connectivity of the silica network, as in the classical picture, although the distribution of non-bridging oxygen is not as uniform as generally assumed. This feature is supported byu recent NMR studies in which Q-species indicate a significant degree of disorder in the arrangement of non-bridging oxygen. Channels are observed in the simulated glasses at both compositions and are associated with lower order Q_n species.