Collaborative Research: First Principles Investigation of Silicate Liquids at Mantle Conditions

该项目将采用基于密度泛函理论的第一性原理方法来研究硅酸盐液体的物理化学性质，硅酸盐液体是地球地幔的主要组成部分。 该方法已被证明是一个理想的补充，实验方法在研究范围广泛的地球材料的晶体性质，在这里它将扩展到模拟的材料系统，涉及相对大量的原子。这些大规模的模拟将导致我们在大范围的压力，温度和成分上对硅酸盐液体的认识取得重大进展，这对于更好地了解行星演化至关重要，因为硅酸盐液体是地球内部热量和质量传输的主要手段。 该项目将为理解以下内容做出重要贡献：a）通过状态方程的从头计算预测硅酸盐液体的浮力，包括透辉石，顽火辉石和镁橄榄石组成的液体在地幔的压力-温度范围内; B）通过分析理论模拟中可用的完整结构信息，包括配位数，键长和键角，分析硅酸盐液体的结构。透辉石和含水钠长石组合物的液体的结构的分析，和熔体上的MgO-SiO2加入预计产生洞察熔体行为的起源，包括压缩机制和混合性能;和c）通过从头计算预测的体积和混合焓作为组合物的函数沿着MgO-SiO2和钠长石-水连接在硅酸盐液体中的混合热力学。该研究实质上是利用计算科学的思想和技术来解决地球物质研究中的挑战性问题。 复杂地球化学和地球物质问题的研究与高端计算之间的相互作用对这两个领域都有好处。 为了充分利用这方面的优势，该项目还将启动Access Grid的应用程序-一种允许组对组多媒体网络通信的设施，以培养学生在这一跨学科的努力。

The project will apply the first-principles approach based on density functional theory (DFT) to investigate the physico-chemical properties of silicate liquids, which are major components of the Earth's mantle. The approach has already been proven to be an ideal complement to the experimental approach in studying a wide range of crystalline properties of the Earth materials and here it will be extended to simulation of material systems involving relative large number of atoms. These large-scale simulations will result in major advances in our knowledge of silicate liquids over the large range of pressure, temperature, and composition that are crucial for a better understanding of planetary evolution, as silicate liquids are primary means of heat and mass transport inside the Earth. The project will make key contributions to understanding of: a) Buoyancy of silicate liquids through ab initio predictions of the equation of state including liquids of diopside, enstatite, and forsterite compositions over the pressure-temperature regime of the mantle; b) Structure of silicate liquids via analysis of the complete structural information that is available in theoretical simulations including coordination numbers, bond lengths, and bond angles. Analysis of the structure of liquids of diopside and hydrous albite composition, and melts on the MgO-SiO2 join is expected to yield insight into the origin of melt behavior including compression mechanisms and mixing properties; and c) Thermodynamics of mixing in silicate liquids through ab initio predictions of the volume and enthalpy of mixing as a function of composition along the MgO-SiO2 and albite-water joins. The proposed research is essentially an exploitation of ideas and techniques of computational science to challenging problems in the investigation of Earth materials. The cross-fertilization between studies of complex geochemical and earth materials issues on the one hand, and high-end computation on the other should be of benefit to both fields. To take full advantage of this aspect, the project will also initiate applications of the Access Grid - a facility that allows group-to-group multimedia network communication, to train students in this interdisciplinary effort.