COLLABORATIVE RESEARCH: Theoretical Investigation of Core Materials

研究人员建议通过计算铁和铁合金的原子尺度物理来更好地了解地核的结构、演化和过程。在这次更新中，他们将以先前的研究成果为基础，应用在早期资助期间开发的快速有效的方法来解决高压地球物理学的重要问题，特别是精确高温特性的计算。各种比全电子线性化增强平面波（LAPW）方法更有效的电子结构方法将被用于高温计算，包括投影混合基方法和总能量紧密结合模型。统计力学方法将包括：1)细胞模型中的粒子，它允许快速计算平衡热力学性质，包括非调和项；2)从头算分子动力学，它允许计算平衡性质，以及输运和缺陷性质。高温下的磁性处理将受到特别关注，因为这在大多数实验数据存在的相对低压状态（1毫巴）中是重要的。研究人员将调查一些对我们了解地球内外核很重要的领域，包括：1)铁的亚固相图；2)固体铁在高温高压下的弹性；3)在低压和高压下固体铁中空位的形成和扩散；4)扩展缺陷和流变性；5)铁的熔化曲线；6)铁液的平衡和输运性质，包括非弹性性质；7)合金元素（包括Ni、O、S、C和H）对液态和固态铁物理性质的影响。

Cohen 9980602 The investigators propose to obtain a better understanding of the structure, evolution and processes of the Earth's core through computations of the atomic-scale physics of iron and iron alloys. In this renewal, they will build on the achievements of prior research by applying fast and efficient methods, developed during earlier grant periods, to problems important to high-pressure geophysics, in particular to the computation of accurate high temperature properties. A variety of electronic structure methods that are more efficient than the all electron linearized-augmented-plane-wave (LAPW) method will be used in high temperature calculations, including a projector mixed-basis method and a total energy tight-binding model. Statistical mechanical methods will include: 1) The particle in a cell model, which permits rapid calculation of equilibrium thermodynamic properties including anharmonic terms, and 2) Ab initio molecular dynamics which allows calculations of equilibrium properties, as well as transport and defect properties. The treatment of magnetism at high temperature will receive special attention because this is important in the relatively low-pressure regime (1 Mbar) where most experimental data exist. The investigators will investigate a number of areas that are important to our understanding of the earth's inner and outer core including: 1) the sub-solidus phase diagram of iron; 2) the elasticity of solid iron at high temperature and high pressure; 3) the formation of vacancies and diffusion in solid iron at low and high pressures; 4) extended defects and rheology; 5) the melting curve of iron; 6) the equilibrium and transport properties of liquid iron including anelastic properties; and 7) the effect of alloying elements (including Ni, O, S, C and H) on the physics of liquid and solid iron.