FeO_(2)与FeO_(2)He晶格热导率与声速特征的第一性原理研究  

First Principles Study of Lattice Thermal Conductivity and Sound Velocity Characteristics of FeO_(2) and FeO_(2)He

作　　者：吴潇 马阳阳 杨述 何开华[1] 姬广富[2] WU Xiao;MA Yangyang;YANG Shu;HE Kaihua;JI Guangfu(Faculty of Maths and Physics,China University of Geosciences,Wuhan 430074,Hubei,China;National Key Laboratory of Shock Wave and Detonation Physics,Institute of Fluid Physics,CAEP,Mianyang 621999,Sichuan,China)

机构地区：[1]中国地质大学(武汉)数学与物理学院,湖北武汉430074 [2]中国工程物理研究院流体物理研究所冲击波物理与爆轰物理重点实验室,四川绵阳621999

出　　处：《高压物理学报》2021年第3期42-48,共7页Chinese Journal of High Pressure Physics

基　　金：国家自然科学基金(41474067)。

摘　　要：高温高压实验研究发现了一种新型铁氧化物FeO_(2),其可以稳定地存在于地球内部。理论研究表明,FeO_(2)可以与He在高温高压下发生反应,形成FeO_(2)He,借此解释了地球内部He的赋存机制。采用第一性原理方法,对比研究了FeO_(2)和FeO_(2)He两种矿物在下地幔条件下的晶格热导率和声速特征。计算结果表明,FeO_(2)He的晶格热导率比FeO_(2)的晶格热导率高很多,并且其随压力的变化也比FeO_(2)大。两种矿物的晶格热导率与温度的变化关系都接近T−1,与传统半导体的结论一致。分析表明,两种矿物的群速度差异较小,对晶格热导率的影响有限;两种矿物的非谐散射率有较大的差异,是导致两者晶格热导率差异的主要原因。FeO_(2)He的剪切和压缩波波速都比FeO_(2)大一些,但两者的波速都比下地幔主要矿物钙钛矿的波速小,符合D″层超低声速的特征。Recent experimental studies at high temperature and high pressure reported a new iron oxide,FeO_(2),which is stable from 74 GPa to the core-mantle boundary(CMB)pressure.Theoretical investigation also indicated that FeO_(2) can react with He at high temperature and high pressure to form FeO_(2)He,which can explain the enigmatic He reservoir in the Earth.In this work,the lattice thermal conductivities and wave velocities of two minerals have been studied using first principles combined with lattice dynamics method.The calculations show that the lattice thermal conductivity of FeO_(2)He is larger than that of FeO_(2),meanwhile,and the pressure dependence of lattice thermal conductivity of FeO_(2)He is stronger than that of FeO_(2).The temperature dependence of lattice thermal conductivity of both minerals is close to T−1 relation,which is similar with those of traditional semiconductor.The group velocities have limited effect on the difference in lattice thermal conductivity between two minerals,and which is determined by the giant discrepancy in the anharmonic scattering rates.The compressive velocity and shear velocity of FeO_(2)He are larger than those of FeO_(2).Their velocities are smaller than the values of perovskite and post-perovskite at the same condition,which implies that FeO_(2) and FeO_(2)He are of the character of ultra-low sound velocity in D"layer.

关 键 词：FeO_(2) FeO_(2)He 晶格热导率 波速 第一性原理 

分 类 号：O521.2[理学—高压高温物理]