Effects of pressure and temperature on thermodynamic properties of WB3 by first-principles predictions

Abstract

In this work, the effects of temperature and pressure on thermodynamic properties of potential ultrahard hP4-, hP8-, hP16- and hR24-WB3 were predicted using first-principles calculations based on density functional theory and using quasi-harmonic Debye model within GIBBS program. Bulk modulus B, thermal expansion coefficient α, Debye temperature Θ, Grüneisen ratio γ and heat capacity Cv and Cp under pressure (P) of 0–30 GPa and temperature (T) of 0–1500 K were investigated. The phonon dispersions and the formation enthalpy in the ground state demonstrated that these WB3 are thermodynamically stable. The thermal expansion coefficient α is more sensitive at the low temperatures than that at high temperatures. Moreover, as the pressure increases, thermal expansion coefficient of each WB3 decreases. The pressure and temperature dependences of Debye temperature Θ are just the opposites of Grüneisen parameter γ.