Pressure-induced phase transitions and electronic structure of GaAs

The structural and electronic properties of GaAs under high pressure have been investigated using an ab initio pseudo-potential approach within the framework of density functional theory. We use the local density approximation based on exchange-correlation energy optimization for calculating the total energy. The phase transition B3 -> B1 -> B2 in bulk GaAs is investigated. Results of the first-principles calculation of the structural phase transition and the electronic properties of GaAs in the three different crystallographic structures are reported. GaAs is found to undergo structural transition from B3 to B1 phase, demonstrating a reasonably good agreement with experimental data. The equation of state for these transformations also shows good agreement with experimental results. The calculated value of volume collapse is close to the observed data. The energy of the B2 phase is found to be slightly higher than that of the B1 phase. A possible mechanism for the B3 -> B2 transition characterized by the space group Pm3m is discussed. The calculated values show that there is a relatively small value of enthalpy for the B3 -> B1 transition as compared to the B3 -> B2 transition, which provides the transition behaviour of GaAs from the kinetic viewpoint. The electronic structures have also been computed at different volumes.