Chin. Phys. B ›› 2014, Vol. 23 ›› Issue (1): 17101-017101.doi: 10.1088/1674-1056/23/1/017101

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

Phase transition and thermodynamic properties of ThO2：Quasi-harmonic approximation calculations and anharmonic effects

李强, 杨俊升, 黄多辉, 曹启龙, 王藩侯   

  1. Computational Physics Key Laboratory of Sichuan Province, Yibin University, Yibin 644000, China
  • 收稿日期:2013-05-06 修回日期:2013-07-05 出版日期:2013-11-12 发布日期:2013-11-12
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 61275203), the Foundation of Sichuan Educational Committee, China (Grant Nos. 13ZA0198 and 13ZB0211), and the Foundation of Science and Technology of Yibin, China (Grant No. 2012SF034).

Phase transition and thermodynamic properties of ThO2：Quasi-harmonic approximation calculations and anharmonic effects

Li Qiang (李强), Yang Jun-Sheng (杨俊升), Huang Duo-Hui (黄多辉), Cao Qi-Long (曹启龙), Wang Fan-Hou (王藩侯)   

  1. Computational Physics Key Laboratory of Sichuan Province, Yibin University, Yibin 644000, China
  • Received:2013-05-06 Revised:2013-07-05 Online:2013-11-12 Published:2013-11-12
  • Contact: Li Qiang E-mail:wslypq@126.com
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 61275203), the Foundation of Sichuan Educational Committee, China (Grant Nos. 13ZA0198 and 13ZB0211), and the Foundation of Science and Technology of Yibin, China (Grant No. 2012SF034).

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摘要： The thermodynamic properties and the phase transition of ThO2 from the cubic structure to the orthorhombic structure are investigated using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon calculations. The anharmonic contribution to quasi-harmonic free energy is accounted for by using an effective method (2010 Phys. Rev. B 81 172301). The results reveal that at ambient temperature, the phase transition from the cubic phase to the orthorhombic phase occurs at 26.45 GPa, which is consistent with the experimental and theoretical data. With increasing temperature, the transition pressure decreases almost linearly. By comparing the experimental results with the calculation results, it is shown that the thermodynamic properties of ThO2 at high temperature improve substantially after including the anharmonic correction to quasi-harmonic free energy.

关键词: first-principles, ThO2, phase transition, thermodynamic property, anharmonic correction

Abstract: The thermodynamic properties and the phase transition of ThO2 from the cubic structure to the orthorhombic structure are investigated using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon calculations. The anharmonic contribution to quasi-harmonic free energy is accounted for by using an effective method (2010 Phys. Rev. B 81 172301). The results reveal that at ambient temperature, the phase transition from the cubic phase to the orthorhombic phase occurs at 26.45 GPa, which is consistent with the experimental and theoretical data. With increasing temperature, the transition pressure decreases almost linearly. By comparing the experimental results with the calculation results, it is shown that the thermodynamic properties of ThO2 at high temperature improve substantially after including the anharmonic correction to quasi-harmonic free energy.

Key words: first-principles, ThO2, phase transition, thermodynamic property, anharmonic correction

中图分类号:  (Density functional theory, local density approximation, gradient and other corrections)

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65.40.-b (Thermal properties of crystalline solids)