中国物理B ›› 2016, Vol. 25 ›› Issue (5): 57102-057102.doi: 10.1088/1674-1056/25/5/057102
• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇 下一篇
Xiao-Lin Zhang(张晓林), Yuan-Yuan Wu(武媛媛), Xiao-Hong Shao(邵晓红), Yong Lu(鲁勇), Ping Zhang(张平)
Xiao-Lin Zhang(张晓林)1, Yuan-Yuan Wu(武媛媛)1, Xiao-Hong Shao(邵晓红)1, Yong Lu(鲁勇)2, Ping Zhang(张平)2
摘要: The high pressure behaviors of Th4H15 and ThH2 are investigated by using the first-principles calculations based on the density functional theory (DFT). From the energy-volume relations, the bct phase of ThH2 is more stable than the fcc phase at ambient conditions. At high pressure, the bct ThH2 and bcc Th4H15 phases are more brittle than they are at ambient pressure from the calculated elastic constants and the Poisson ratio. The thermodynamic stability of the bct phase ThH2 is determined from the calculated phonon dispersion. In the pressure domain of interest, the phonon dispersions of bcc Th4H15 and bct ThH2 are positive, indicating the dynamical stability of these two phases, while the fcc ThH2 is unstable. The thermodynamic properties including the lattice vibration energy, entropy, and specific heat are predicted for these stable phases. The vibrational free energy decreases with the increase of the temperature, and the entropy and the heat capacity are proportional to the temperature and inversely proportional to the pressure. As the pressure increases, the resistance to the external pressure is strengthened for Th4H15 and ThH2.
中图分类号: (Density functional theory, local density approximation, gradient and other corrections)