Calculation of mineral properties with the electron gas model

Abstract

The inclusion of non-spherical distortions of the ions, or equivalently covalent bonding effects, in the electron gas model leads to improved results for the properties of minerals. For crystals which have open structures, the structures, energies and compressibilities calculated with the distorted ion model are in much better agreement with experiment than those calculated with spherical ion model; the improved structures are due mainly to smaller and more accurate cation-anion-cation bond angles and the improved energies are due to the stronger bonds formed when charge density moves into the bonding regions. For crystals which have close-packed structures, the structures and compressibilites are modeled well with the spherical ion model, but the energies are calculated more accurately with the distorted ion model. The distorted ion model leads to improved modeling of pressure-induced phase transitions, due to the more accurate calculation of the crystal structures, compressibilities and energies.