Effect of high pressure on polymorphic phase transition and electronic structure of XAs (X=Al,Ga, In)

The structural and electronic properties of XAs (X = Al, Ga, In) under pressure have been investigated using ab-initio pseudo-potential approach within local density approximation in B3→B1→B2 phases. The values of phase transition pressures show reasonably good agreement with the experimental data and better than others. The B1→B2 phase transition in InAs is not seen. The volume collapse computed from equation of state (EOS) is found to be in good agreement with the experimental values. Under ambient conditions, the energy of B3 phase is lowest as compared to other phases, while at high pressures beyond B1→B2 phase transition, the energy of B2 phase is found to be lower than that of B1 phase showing correct stability of the phases. There is relatively smaller enthalpy associated with B3→B1 transition as compared to B3→B2 transition. The electronic structures have also been computed at different pressures. We have also reported the effect of pressure on energy gap and valence band width.