Applications of ab initio Quantum Mechanical Potential Surfaces to Mineral Physics Calculations

Abstract

Recent studies have reported on the use of ab initio potential surfaces using a range of basis sets from a minimal STO-3G to a robust 6-31G* in the solid state physics of minerals and mineral surfaces (Lasaga, 1993, and reference therein). This paper explores the effects of electron correlations on the ab initio calculations and also expands the application to other mineral physics calculations such as albite and corundum by choosing the appropriate molecular clusters. Ultimately, the understanding of bonding and atomic processes in minerals will have to be based on extensive use of quantum mechanical calculations. One of the central aims of these calculations is to establish at what level ab initio quantum mechanical calculations can serve as a framework for the studying of the physics and chemistry of minerals. In particular, one must consider the effect of the size of the molecular clusters, the size of the basis sets,as well as the effects of electron correlation on the various properties being calculated. In addition, the representation of the quantum mechanical potential surface data by a potential that is easily used by others in molecular dynamics or mineral physics calculations, is another important problem. We will discuss some new representations involving the so-called EPEN/2 or QPEN potentials. SiO2