- Webb 1100
Title: Thermodynamics of Liquid and Glassy Na-Ca Aluminosilicates
Abstract: Thermodynamic properties (e.g., energy, pressure, volume) of silicate liquids are essential to many large-scale questions in mineralogy, petrology, and geochemistry. Physical, chemical, and thermal properties of silicate liquids at high pressure are also important factors in planet-forming processes such as bolide impacts, partial melting, and the cooling of magma oceans. While laboratory experiments are the gold standard for quantifying thermodynamic and material properties, the vast majority of these data are limited to low pressure and relatively low temperature (< 2000 K). Molecular dynamics (MD) simulation is a statistical-mechanics method for calculating thermodynamic and transport (e.g., viscosity, ionic diffusion) properties of materials and has no physical constraints to achieve the temperature or pressure of interest. The MD method directly calculates the atomic arrangement (or microscopic structure) of the liquid, which can be analyzed concomitantly with macroscopic properties (e.g., thermodynamic) to provide a sound connection between the properties of silicate melt and the atomic-scale structure. I use MD simulations to investigate the liquid thermodynamics of Na-Ca aluminosilicates in four general areas: (1) developing an equation of state for high-pressure liquid NaAlSi3O8 (albite composition); (2) investigating the dynamics during super-cooling of liquid NaAlSi3O8 through the glass transition; (3) analyzing thermodynamic mixing lines at high pressure across the plagioclase compositional join; and (4) determining the compositional dependence of thermal conductivity for plagioclase melt. Structural properties are also presented with respect to thermodynamic changes in liquid NaAlSi3O8. This talk highlights a broad range of questions that MD simulations can solve and presents some versatile techniques available for studying thermodynamic properties beyond the limits of laboratory methods.