INVESTIGATION OF THERMODYNAMIC PROPERTIES AND ANISOTROPIC FACTORS OF PERFECT AND DEFECTIVE TUNGSTEN THROUGH CORRELATION WITH ELASTIC CONSTANTS: A MOLECULAR DYNAMICS STUDY

Abstract

In this study, the thermodynamic properties and anisotropic factors of perfect and defective tungsten were investigated through their correlation with elastic constants. The study examined sound velocities, Debye temperature, minimum thermal conductivity, melting point, and elastic anisotropy factors at various temperatures and pressures. The utilized elastic constants were calculated by molecular dynamics simulations. We used three different interatomic potentials in the simulations involving two embedded atoms and one modified embedded-atom method. The findings indicated that temperature and pressure were positively correlated with anisotropic factors, with increased values leading to an increase in metal anisotropy. Also, defects were found to cause an increase in anisotropy, with a single vacancy having a greater impact on elastic anisotropy compared to a central void in the crystal structure. The study also found that the fundamental thermodynamic characteristics of pure tungsten crystal including density, sound velocities, Debye temperature, and Grüneisen parameter in the ambient conditions for all three potentials were in good agreement with previous experimental and theoretical calculations. The results showed that defective structures displayed the same trend as perfect crystals for elastic constant-related properties. The presence of defects in the crystal caused a decrease in thermodynamic properties at all temperatures and pressures, with the degree of decrease directly correlated with the fraction of crystal defects. The study also found that the minimum thermal conductivity as a key parameter of tungsten showed a downward trend with temperature and upward with pressure.