STRUCTURE-STABILITY RELATIONSHIPS FOR ALL-SILICA STRUCTURES

We will discuss predictions for the stability and structures of all-silica zeolitic structures. We will show that we have derived a shell-model potential, based on ab initio calculations, which gives good predictions for the structure and stability of all-silica structures. We will compare three shell-model predictions with two rigid-ion model predictions for the structure and stability of silicates. We will show that shell-model predictions for the relative stability of zeolites are much closer to experiment than rigid-ion model predictions, due to the canceling of covalent and electrostatic terms in the shell models which does not occur in the rigid-ion models. Using the potentials with the highest predictive power on both stabilities and structures of silicates we will discuss structure-stability relationships that have been proposed in the literature.