9627458 Gibbs This project is designed to advance work in three fields: mineralogy, crystallography and geochemistry. Recent advances by the investigators have resulted in a determination of crystal structures, space group symmetries and cell dimensions. Software, developed by the investigators, was used to derive more than 85 distinct stable and metastable framework silica structure types employing a potential energy function created from quantum mechanical calculations. An examination of the structure and the potential energy functions used in the derivations will improve the understanding of the forces that bind the structures together and clarify the role that these forces play in governing the atomic arrangements and the symmetries of the resulting phases. The calculations will also provide a catalog of structure types that will facilitate the identification of any new structure types that are discovered either in the laboratory or in nature. First principle crystal calculations will be used to generate structures for the new low energy structure types derived in this study. It is anticipated that this information will increase the understanding of the connection between potential energy and structure thereby enhancing the understanding of the role that the binding forces and the electron density distributions play in determining structure. An analysis will be completed of the electron density distributions calculated for the bonds of a variety of hydroxyacid molecules in an attempt to relate the fractional ionic character of the bonds in these molecules to the electron density and the local kinetic and potential energy densities at the bond critical points. One of the benefits of this study is that it could lead to improved models and strategies for the synthesis of new porous tectosilicates, materials that have found use in the beneficiation and generation of petroleum products. Another benefit is that the calculations could produce a collection of dense silica structure type s with 6-coordinate Si, phases which would be of importance in geophysical research.
