含铁后钙钛矿的热传导特征研究：对D层热结构的启示

项目名称： 含铁后钙钛矿的热传导特征研究：对D层热结构的启示

项目编号： No.41474067

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 天文学、地球科学

项目作者： 何开华

作者单位： 中国地质大学（武汉）

项目金额： 85万元

中文摘要： 后钙钛矿的发现为解释D″层特殊的物理、化学和地震波等特征提供了一条新途径，因此吸引了多个学科的注意。后钙钛矿晶格热传导性质决定了来自地核的热流大小，与D″层的稳定性及地幔柱的形成有着密切的联系，同时也影响着地幔和地核长期的热演化进程和地磁场的产生等地质过程。因受实验技术的限制，对其热传导特征认识不足，尤其是含铁对热传导的影响。本项目拟采用第一性原理分子动力学结合晶格动力学计算方法，在模型上考虑铁作为杂质存在于后钙钛矿中，并且引入原子无序及同位素效应，系统研究铁的价态、自旋和含量对后钙钛矿的热传导特征的影响机制；探讨相变(钙钛矿至后钙钛矿)对D″层热流的影响；计算D″层矿物混合组分(20%方镁石与80%后钙钛矿)的平均热导率及热流值，给出热导率随温度和压强变化的分布函数。该项目的实施能够为合理的建立D″层热结构提供关键的物理依据和约束条件，同时为地球演化和地球动力学研究提供一定的理论依据。

中文关键词： 高温高压；后钙钛矿；热导率；第一性原理；D层

英文摘要： The discovery of post-perovskite has been accepted as a new way to explain the special physical, chemical and seismic properties of D″ layer, thus much attention is attracted to this field. The lattice thermal conductivity of post-perovskite determines the magnitude of heat flux from the core, and is intimately related to stability of the boundary layer and the formation of mantle plumes, the longterm thermal evolution of both mantle and core, and the driving force for generation of the geomagnetic field. However, due to the limitation of experimental techniques, its lattice thermal conductivity is short of knowledge, especially for the effect of iron on thermal conductivity. This proposal will apply first principles molecular dynamics combined with lattice dynamics method, and the iron as an impurity in the minerals of mantle will be considered, and the disorder and isotope effects will be induced. The effects of valence states, spin states and contents of iron on thermal conductivity of post-perovskite will be studied, and the effect of phase transition from perovskite to post-perovskite on thermal structure of D″ layer will be discussed. The average thermal conductivity and thermal flux of the mixture of two minerals (Periclase and Post-Perovskite) will be calculated. This study can provide key physical basis and critical constraints for D″layer to establish a reasonable thermal structure, and also provide a theoretical basis for the evolution of the Earth and geodynamics.

英文关键词： high temperature and high pressure;post-perovskite;thermal conductivity;first principles;D layer