A Study of the Incorporation of Water in Earth Materials Based on Electron Density Distributions

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Ross EAR-0229472 Research will be undertaken to advance the geochemist's - mineralogist's understanding of the mechanisms controlling the incorporation of water in earth materials and properties of the bonded interactions, both in minerals and representative molecules. Sites that are susceptible to electrophilic attack will be located, at the atomic level, within the crystal structures and on the surfaces of minerals. These calculations will identify potential sites for incorporation of hydrogen in nominally anhydrous minerals, both as hydroxyl groups and as water molecules. In addition, the adsorption and alignment of molecules like water, the hydronium and hydroxyl ions within the structures will be determined. These goals will be accomplished by evaluating the bond critical point properties of the calculated electron density distributions for a wide variety of minerals. The properties of the electron density will be determined and the local maxima in the Laplacian distributions for the valence shell electrons of the bonded atoms will be located. Electron density distributions will also be studied at pressure to monitor how these sites behave when compressed. A knowledge of the location and structure of the internal and surface sites that are susceptible to electrophilic attack will advance our understanding, at the atomic level, of the incorporation of hydrogen in minerals as well as the chemical reactivities of silicates and oxides. It is further anticipated that this work will not only provide a theoretical basis for the modeling of internal and surface reactions of earth materials, but that it will lead, in future studies, to a better understanding of the atomistic properties and pathways involved in weathering, bacterial attack, chemisorption and other important geochemical processes.