First-Principles Study Of Tungsten Copper And Tungsten Molybdenum Alloys In High Temperature And Pressure

Tungsten (W) based alloys, due to their high melting point, high-density, low thermal expansion coefficient, good electrical and thermal conductivity and superior corrosion resistance, is widely used in defense industry. The electronic structures, elastic properties and thermodynamic properties of copper tungsten alloys and disordered solid solution phase MoW alloys are investigated by using the first-principles calculation method based on density function theory. The main conclusion can be summarized as follows:1. The electronic structure, elastic properties and the phonon spectrums of three different proportions of copper tungsten alloys at ground state, high temperature and high pressure are calculated, which indicates that Cu3W is an unstable structure and the CuW and CuW3 are stable structures. The quasi harmonic Debye model and the quasi harmonic approximation (QHA) model are employed to calculate the specific heat of the CuW alloys. In contrast, the quasi harmonic approximation model is more accurate.2. The structure, elastic, and thermodynamic properties of disordered MoxW1-x alloys are systematically studied by using the first-principles phonon calculations and the quasi-harmonic approximation method. To obtain the bcc solid solutions, the 16-atom special quasi-random structures (SQSs) to model the disordered phases. The calculated elastic constants show that all the considered phases are mechanically stable. The elastic sound velocities and Debye temperature both decrease with the increase of Mo ratio. Phonon dispersions of these alloys are firstly presented. Based on the phonon frequencies, thermodynamics such as Gibbs free energy, entropy, and heat capacity are obtained by quasi-harmonic approximation.