Theoretical studies of BAs at high pressure have so far been mainly limited to the consideration of the phase with rocksalt structure . Wentzcovitch et al. have studied the relative stability of different BAs phases using the total-energy pseudopotential technique and reported structural transition from fourfold coordinated zinc-blende (zb) phase to sixfold coordinated rocksalt (rs) phase at 110 GPa. According to other works , the transition pressure varies from 93 GPa to 134 GPa . However, this transition has never been observed experimentally; on the contrary, it was found that BAs undergoes a collapse from the zinc-blende phase to an amorphous state at pressures above 125 GPa . As for the hypothetical high-pressure phases with β-Sn and CsCl structure, they were found to be less energetically favorable than the rocksalt phase of BAs .