Insight into the phase transition, elastic and thermodynamic properties of BeS compound under high pressure and temperature from the first principle calculation

Abstract

Based on the first principle plane wave pseudopotential and generalized gradient approximation (GGA) method, the phase, elastic and thermodynamic properties of BeS compound at pressure ranging from 0 to 175 GPa are calculated. After studying the energy-volume and entropy difference-pressure of the zinc blende, NiAs, NaCl and CsCl structures of BeS compound in depth, we consider the zinc blende and NiAs structures as two stable structures for BeS compound. The phonon spectra and elastic constants reveal that zinc blende and NiAs structures are also structurally and mechanically stable at ambient conditions. Furthermore, the phase transition pressure from zinc blende structure to NiAs structure is 58.615 GPa. Intriguingly, the anisotropies of the elastic and sound velocities of BeS are found to exhibit anisotropic characteristics, which is the first comprehensive study on the mechanical properties of BeS compound. Notably, we report for the first time the thermodynamic properties of NiAs structure, such as the Debye temperature, specific volume heat capacity, which shows great potential in the further study on the properties of BeS compound.