高压下钨弹性和热力学性质的第一性原理研究

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

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。

The elastic constants 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 a-greement with the experiment values at ambient pressure.The high pressure elastic constants indicate 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 stud-ied and it is found that bcc phase W is ductile.Based on the 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.