EAPSI: Evaluating the Melting and Vibrational Properties of Phase H as a Function of Pressure

EAPSI：评估 H 相的熔融和振动特性与压力的函数关系

• 批准号: 1612833
• 负责人: Elizabeth Thompson
• 金额: $ 0.04万
• 依托单位: Thompson Elizabeth C
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2017-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1612833&HistoricalAwards=false
• 关键词: EAPSI; Evaluating; Melting; Vibrational; Properties

Forty years of scientific literature on the topic has produced wildly variable estimates of the water content within the deep Earth--with values ranging from a quarter to four times the volume of water found in Earth's oceans. The recent discovery of hydrous 'phase H' (MgSiO4H2) provides a new insight into the distribution of water in the Earth's interior. Determining the stability of hydrous phases such as phase H aids in constraining the quantity of water in the lower mantle, a region of the Earth almost 100 times more massive than the crust. The formation of phase H was first predicted in a computational study by Dr. Jun Tsuchiya of the Geodynamics Research Center (GRC) at the University of Ehime, Japan. Dr. Tsuchiya will lend her expertise using first-principles techniques to study high-pressure hydrous phases to this project and the GRC will provide use of a supercomputer that will enable the timely completion of this project.This proposal aims to provide critical insight into the deep Earth's hydrogen budget via three ab initio investigations into key hydrous mantle phases: (1) modeling the melting behavior of phase H as a function of pressure, (2) modeling the melting curve of d-AlOOH, and (3) first-principles calculations of the vibrational properties of phase H as a function of pressure. The melting curves of phase H and d-AlOOH will be determined using a first principles molecular dynamics technique. This type of calculation enables the determination of thermodynamic properties by numerically modeling the interatomic potentials between particles in the system of interest. Vibrational properties of phase H will be calculated using first-principles calculations based on a generalized gradient approximation to the exchange-correlation functional. These calculations are complementary to the principal investigator?s experimental efforts to investigate hydrous phases under extreme conditions and will help constrain the water budget of the Earth's deep interior.This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.

四十年来，关于这一主题的科学文献对地球深处的水含量做出了截然不同的估计，其数值范围为地球海洋中水量的四分之一到四倍。最近发现的含水“H 相”(MgSiO4H2) 为了解地球内部水的分布提供了新的见解。确定 H 相等含水相的稳定性有助于限制下地幔中的水量，下地幔是地球的一个区域，其质量几乎是地壳的 100 倍。日本爱媛大学地球动力学研究中心 (GRC) 的 Jun Tsuchiya 博士在一项计算研究中首次预测了 H 相的形成。 Tsuchiya 博士将利用她的专业知识，利用第一原理技术来研究高压含水相，GRC 将提供超级计算机的使用，使该项目能够及时完成。该提案旨在提供对这一项目的批判性见解。通过对关键含水地幔相进行三项从头算研究，了解地球深层的氢收支：(1) 模拟 H 相的熔化行为作为压力的函数，(2) 模拟 d-AlOOH 的熔化曲线，以及 (3)作为压力函数的 H 相振动特性的第一性原理计算。 H 相和 d-AlOOH 的熔化曲线将使用第一原理分子动力学技术来确定。这种类型的计算可以通过对感兴趣系统中粒子之间的原子间势进行数值建模来确定热力学性质。 H 相的振动特性将使用基于交换相关函数的广义梯度近似的第一原理计算来计算。这些计算是对首席研究员在极端条件下研究水相的实验工作的补充，并将有助于限制地球内部深处的水预算。东亚和太平洋夏季研究所计划下的该奖项支持美国研究生的夏季研究学生，由 NSF 和日本学术振兴会共同资助。