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

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.