W热力学性质和弹性性质的第一性原理研究

First Principles Studies of Thermodynamic Properties and Elastic Properties of Cubic Tungsten

使用第一性原理方法结合准谐近似理论研究了立方结构钨的热力学性质,包括平衡体积V、体弹模量B0、线膨胀系数α、熵S、振动自由能F、等压热容CP和等容热容CV随温度的变化关系。在计算体系的线膨胀系数、熵、振动自由能、等压热容和等容热容时考虑了热电子和热振动对自由能的贡献。计算结果表明:考虑热电子对自由能贡献后得到的线膨胀系数、熵、振动自由能和等压热容在0～2000 K范围内均与实验值符合较好。在得到平衡体积随温度变化的基础上,计算了钨立方结构的弹性性质,得到了弹性常数、体积模量、剪切模量和杨氏模量随温度的变化关系,所得结果与实验测量值符合较好。

The thermodynamic properties of cubic tungsten were studied by first principles combined with quasiharmonic approximation, including the temperature dependence of equilibrium volumes, bulk modulus, linear thermal expansion coefficient, entropy, helmholtz free energy, heat capacity at constant pressure and heat capacity at constant volume. The electronic contribution and lattice vibrational contribution to free energy were taken into account when linear thermal expansion coefficient, entropy, helmholtz free energy, heat capacity at constant pressure and heat capacity at constant volume were calculated. The results show the calculated linear thermal expansion coefficient, entropy, helmholtz free energy, heat capacity at constant pressure and heat capacity at constant volume with taking into account the electronic contribution are in good agreement with experimental measurements for temperatures up to 2000 K. On the basis of the above results, elastic properties of cubic tungsten are obtained. The temperature dependences of elastic coefficient, bulk modulus, shear modulus and young＇s modulus are also got, which are in good agreement with experimental data.