1ST PRINCIPLES METHODS FOR STRUCTURAL TRENDS IN OXIDES - APPLICATIONS TO CRYSTALLINE SILICA

One goal of crystal chemistry is to construct approaches to compute from ''first principles'' the structural properties of ordered compounds. Such an approach is particularly valuable for families of structures with a given stoichiometry. An example of this case is crystalline silica. SiO2 may exist in a variety of structures which are nearly identical in terms of binding energies. We will illustrate how first principles methods may be employed to predict the relative stability of silica polymorphs, and how these forms may transform under pressure to other ordered, or disordered, phases. Our methods are based on ab initio pseudopotentials constructed within the local density approximation. These pseudopotentials have been optimized for use with a plane wave basis and should be widely applicable for determining the crystal stability of silicates and related materials.