Silica Under Water Attack: Surfaces, Defects, and Nano-Structures

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TECHNICAL SUMMARY:This award supports theoretical research and education into understanding the physical principles underlying processes in silica-water systems at macro- and nano-scale. The strength of silica-water interactions ranges from van der Waals to covalent depending on local mechanical and chemical conditions. External or internal stress also plays a vital role in modifying the interaction. The mechanical and optical properties of silica in aqueous environments and electronic structures at the water-silica interface are entangled. Large-scale computer simulations based on first principles are powerful tools for predicting materials behavior. This research develops theoretical descriptions of (1) stability of dry quartz surfaces and solid-to-liquid transition of water on silica surfaces, (2) surface defects and optical properties modified by adsorbed molecules or nano-clusters and water, and (3) silica nano-pores and channels filled with water and phenomena due to nanoconfinement and stress. The second phase of the research consists of (1) improving models for interfaces between quantum and classical regions, (2) constructing a computing architecture to integrate modern computer codes for parallel computing, and (3) implementing the quasi-particle self-consistent so-called GW method. The effort undertaken has broader impacts with both scientific and educational consequences. The research includes implementing the GW method in a general public license (GPL) electronic structure code so that it is freely available to the larger scientific community. Educationally, students will receive training in the application of both analytical and computational skills and the research helps develop broad interest and skills in the frontiers of electronic structure calculations and multiscale modeling. Aspects of the research, particularly the underlying computational techniques, form part of the subject matter of the advanced physics course ''Physical modeling and simulation'' developed by the PI at her university.NONTECHNICAL SUMMARY:This award supports theoretical research and education into understanding the physical principles underlying processes in silica-water systems. Silica is a simple molecule with one atom of silicon and two atoms of oxygen bound together. The material is common in nature being recognized as sand or quartz. It is a principal component of glass and substances such as concrete. Silica is the most abundant mineral in the earth's crust. Similarly, water is one of most abundant molecules on the Eath's surface. The proposal research helps understand the complex interactions between these two common materials. Researchers will use theoretical and computational tools to study the electronic structure of water on silica surfaces and will be able to investigate the chemical processes that then take place. Large-scale computer simulations based on first principles are powerful tools used for predicting the materials behavior. The effort undertaken has broader impacts with both scientific and educational consequences. The research includes implementing the computational methods in a computer code that it is freely available to the larger scientific community. Educationally, students will receive training in the application of both analytical and computational skills and the research helps develop broad interest and skills in the frontiers of electronic structure calculations and multiscale modeling. Aspects of the research, particularly the underlying computational techniques, form part of the subject matter of the advanced physics course ''Physical modeling and simulation'' developed by the PI at her university.