Thermal equation of states for body-centered cubic tungsten using extended analytic embedded-atom model

Abstract

Abstract Here the thermal equation of states (EOS) for body-centered cubic (bcc) tungsten (W) is evaluated using embedded atom method (EAM). To reproduce the materials properties under high pressure and high temperature reasonably well, we extend EAM by improving the analytic expressions of the functions of electron density and embedding energy based on the quantum-mechanical results of the electron density distribution and the energy variation with respect to the electron density. Then we determine the parameters of the extended analytic model for bcc W. We evaluate volume dependence of structure energy, elastic properties as function of volume, monovacancy and divacancy properties, lattice vibration at various volumes, and variation of the Gibbs free energy with respect to temperature, pressure and volume within the framework of the quasiharmonic approximation. By minimizing the Gibbs free energy, we determine the thermal EOS, variation of volume or lattice parameter with respect to pressure and temperature. The linear thermal expansion coefficient as function of temperature under different pressures is also evaluated. All calculation results fit well to the experimental and other reliable theoretical calculation results, showing the reliability of the extended analytic EAM in the extended domains of electron density, atomic volume, temperature and pressure.