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Magnetism and Sound Velocities of Iron Carbide (Fe3C) under Pressure
Zhao-yi Zeng*1,2, Cui-e Hu1,2, Xun Liu3, Ling-cang Cai2
1.College of Physics and Electronic Engineering, Chongqing Normal University, Chongqing 400047, China;2.National Key Laboratory for Shock Wave and Detonation Physics Research, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900, China;3.Institute of Pulsed Power Science, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan
Abstract:
The elastic property and sound velocity of Fe3C under high pressure are investigated by using the spin-polarized generalized gradient approximation within density-functional theory. It is found that the magnetic phase transition from the ground ferromagnetic (FM) state to the nonmagnetic (NM) state occurs at ~73 GPa. Based on the predicted Hugoniot of Fe3C, we calculate the sound velocities of FM-Fe3C and NM-Fe3C from elastic constants. Compared with pure iron, NM-Fe3C provides a better match of compressional and shear sound velocities with the seismic data of the inner core, supporting carbon as one of the light elements in the inner core.
Key words:  Alloy, Sound velocity, Density functional theory
FundProject:
高压下Fe3C的磁性和声速性质
曾召益*1,2, 胡翠娥1,2, 刘勋3, 蔡灵仓2
1.重庆师范大学物理与电子工程学院,重庆 400047;2.中国工程物理研究院流体物理研究所冲击波与爆轰物理国防科技重点实验室,绵阳 621900;3.日本熊本大学脉冲功率科学研究院,熊本 860-8555
摘要:
采用基于密度泛函理论的包含自旋极化效应的广义梯度近似方法研究了Fe3C的高压弹性和声学性质. Fe3C在压力作用下由铁磁基态转变到非磁性的高压态,相变压力约为73 GPa. 计算了Fe3C 的Hugoniot线,并根据沿Hugoniot线的弹性常数计算了铁磁状态和非磁性状态的声速. 对比Fe单质,非磁性Fe3C 的压缩波和剪切波声速与地核的地震波数据更为接近,证实了C元素是构成地核的一种成分.
关键词:  合金,声速,密度泛函理论
DOI:10.1063/1674-0068/27/03/297-301
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