Zero-Point Effects on Phase Transitions of Thorium Dihydride under High Pressure
Zero-Point Effects on Phase Transitions of Thorium Dihydride under High Pressure
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DOI：
10.1021/acs.jpcc.5b03195
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发表时间：
2015-06
影响因子：
3.7
通讯作者：
Chao Zhang;Shu-ping Guo;Hong Jiang;G. Zhong;Yue Su
中科院分区：
文献类型：
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作者：
Chao Zhang;Shu-ping Guo;Hong Jiang;G. Zhong;Yue Su
用无偏结构搜索法结合从头算研究了二氢化钍（ThH 2）在压力下的晶体结构.在200 GPa以下，ThH 2的热力学基态存在三个低焓相，包括实验观测到的I4/mmm相和两个新预测的单斜相（C2/m和C/2c相）. ThH 2在没有零点效应的情况下发生I4/mmm → C2/m → C/2c相变，而在有零点效应的情况下，ThH 2直接从I4/mmm相变到C2/c相变。声子计算表明，这些竞争相是热力学稳定的。随着压力的增加，化学键合的金属特性增强。我们的研究结果突出了ZP效应在金属硫化物高压行为中的作用，并为进一步研究压力下含轻元素的其他化合物提供了见解。
The crystalline structures of thorium dihydride, ThH2, under pressure are investigated by using an unbiased structure searching method coupled with ab initio calculations. Three low-enthalpy phases are found as the thermodynamic ground states of ThH2 up to 200 GPa, including an experimentally observed I4/mmm phase and two newly predicted monoclinic phases (C2/m and C/2c phase). ThH2 is predicted to undergo I4/mmm → C2/m → C/2c phase transitions without zero-point (ZP) effects, whereas it directly transforms from the I4/mmm phase to the C2/c phase with ZP effects. Phonon calculations show that these competitive phases are thermodynamically stable. There is a strengthening of the metallic characters of the chemical bonding with increased pressure. Our results highlight the role of ZP effects in the high-pressure behaviors of metal hydrides and provide insight into further studies of other compounds containing light elements under pressure.