高压下钨弹性和热力学性质的第一性原理研究

本文利用密度泛函理论研究了高压下bcc结构钨的弹性和热力学性质，计算得到钨的晶格常数、体弹模量以及其对压强的一阶偏导与实验值符合较好；在常压下弹性常数计算值与实验值符合较好的基础上，预测了其高压数据.针对钨的固相结构稳定性问题，根据力学稳定判断标准得到0~600 GPa范围内bcc结构是力学稳定的.此外，通过体模量和剪切模量的计算得到bcc结构钨在压力低于600 GPa时的力学性能表现为韧性.最后，基于准简谐德拜模型，成功预测了钨的热膨胀系数、等压热容、等容热容和熵随着压强和温度的变化关系，为钨及其合金的进一步设计及应用提供参考.

Ab initio calculation of elastic and thermodynamic properties of W under high pressure

The elastic constant and thermodynamic properties of bcc phase tungsten (W) under high pressure have been investigated with the density functional theory. The calculated equilibrium structural parameters agree well with the available experimental and theoretical values. The calculated elastic constants are in excellent agreement with the experiment values at ambient pressure. The high pressure elastic constant indicates that bcc phase W is mechanically stable with the applied pressure. The pressure dependences of the Bulk modulus B and shear modulus G are all successfully obtained. The ratio of bulk modulus to shear modulus (B/G) has been studied and it is found that bcc phase W is ductile. Based on quasi-harmonic Debye model, the thermodynamic properties including the thermal expansion coefficient, heat capacity and entropy are predicted. This study is helpful for designing and developing W and its alloys.