Phase stability and physical properties of BAs and BP compounds: An ab-initio study

In this study, density functional theory (DFT) calculations were performed to investigate the structural stability of different crystallographic phases, the pressure-induced phase transition, the electronic and thermal properties of BAs and BP compounds. The zinc blende (B3), wurtzite (B4), NaCl (B1), CsCl (B2), NiAs (B8), crystal structures are considered. The Perdew-Wang local density approximation (LDA), the Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) and the newly form (WC) of the generalized gradient approximation (GGA) that was proposed by Wu and Cohen are used to treat the exchange-correlation terms. Moreover, the modified Becke-Johnson (mBJ) scheme is also applied for the band structure calculations. At zero pressure, our findings show that the zinc blende structure is the most stable phase adopted by these compounds. The transition pressure between the various phases is calculated. The band structure calculations reveal a metallic behaviour in NaCl, CsCl and NiAs structures whereas for the other structures, a semiconducting behaviour is observed. The quasi-harmonic Debye model has been used to explore the temperature and pressure effects on the thermal properties for both the compounds.