AN INVESTIGATION INTO THE EFFECTS OF ION INCORPORATION ON THE ELECTRONIC-STRUCTURE OF SILICATE FRAGMENTS VIA AB-INITIO COMPUTATIONAL TECHNIQUES

We investigate the changes in both the geometry and electronic structu re of silicate fragments in response to the pressure of cations. In pa rticular we focus on the double 4 ring, where the encapsulation of a F - anion, produces a transfer of appreciable electron density from the anion onto the framework silicon atoms, while on inclusion of a Na+ ca tion, electron density is transferred from the framework species onto the cation. Analysis of the Mulliken populations has identified that t he Si atoms act as electron density sinks for such electron density tr ansfer. Hydroxyl groups perturb the framework in a way which depends o n the orientation of the hydroxyl molecule.