Disorder and Dynamics in Silicate and Aluminosilicate Liquids, Glasses and Crystals Relevant to Geochemical Processes: Nuclear Magnetic Resonance Studies

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The focus of this research program is the atomic-scale structure and dynamics of the silicate minerals, glasses and magmas that are at the center of most geological processes, from those taking place at the Earth's surface to those in the planet's deep interior. The ultimate goal of this work is to improve fundamental understanding, and eventually enable better prediction, of the material properties that ultimately control complex processes in nature, many of which have enormous impacts on people and on society. For the three-year grant period, one emphasis will be on the effects of high pressure on the structure and properties of silicate melts that represent magmas in the Earth, and hence are tied to many geological processes including the formation and eruption of volcanoes. A second major activity will be further development and application of methods to measure the distribution of minor and major elements in some of the most important silicate minerals in the Earth's crust and mantle, in order to improve models that describe their chemical behavior in nature, and thus better our ability to glean clues about geological evolution from natural samples. Results and methods developed in this project should continue to be of major interest outside of the Earth sciences, particularly for researchers working to develop and optimize silicate glasses and ceramics for advanced technologies, such as materials for data processing and transmission, computer displays, substrates for photovoltaics, fuel cells, and many other applications. Education is central to this project, since most of the research will be part of the training of Ph.D. and postdoctoral students on their ways to careers in science and engineering.The approach taken in this research is to identify important problems where critical details of short- to intermediate-range structure are needed and can be elucidated by laboratory measurements, collect accurate data on synthetic or natural materials, and determine the consequences of the results for key chemical and physical parameters. The most important experimental approach that will be used is solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, which can reveal quantitative details about the structure around many of the components common in minerals and magmas, such as silicon, aluminum, oxygen, phosphorus, and sodium. A variety of compositions of glasses (representing the high temperature molten materials in natural magma systems) and crystalline materials will be synthesized, and measurements made of how their structures change with composition, temperature and pressure. One particular emphasis will be to continue to extend the applicability of NMR, traditionally used to look at abundant constituents of non-magnetic materials, to minor and even trace components and to materials containing substantial amounts of magnetic components. These data should be particularly important in helping to develop more accurate, physically-based models of mineral and magma properties and behavior, which are especially important in the Earth sciences, as many processes take place in regimes of temperature, pressure, and time that are inaccessible to direct observation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.