中文摘要：

在平面波赝势密度泛函理论的框架下,利用广义梯度近似（GGA）计算了体心立方（bcc）和双层密排六方（dhcp）结构的Mo在不同体积下的总能和焓值,算得的等温压缩线与前人的计算结果符合较好。对焓值作差,预测了620GPa压强附近bcc→dhcp的结构相变。根据声子谱的计算结果可知,在高压下,bcc结构可能会向dhcp或9R结构转变。力学稳定性的计算结果进一步显示,在620GPa以上,dhcp-Mo是能够稳定存在的相。结合准谐德拜模型研究了Mo在高压下的热力学性质,计算结果表明,在620GPa附近,bcc和dhcp结构Mo的热力学性质并无显著差异。

英文摘要：

The total energy and enthalpy of bcc-and dhcp-Mo with different volumes were calculated using the generalized gradient approximation（GGA）within the framework of plane wave psudopotential density functional theory.Our calculated isotherms agree well with the previous results.Based on the comparison of enthalpy of bcc and dhcp structures,a bcc→dhcp structural transition was predicted.According to the results of phonon dispersions,the bcc phase may change into dhcp or 9Rstructures under high pressure.The calculations of mechanical stability also confirm that the dhcp structure is stable under pressures that are above620 GPa.We also studied the thermodynamic properties of Mo such as Debye temperatures,isochoric heat capacity,and thermal expansion with the quasi-harmonic Debye model.Our calculated results show that the thermodynamic properties of bcc and dhcp structures do not differ significantly around 620 GPa.