First-principles calculations for transition phase and thermodynamic properties of GaAs

The transition phase of GaAs from the zincblende (ZB)structure to the rocksalt (RS) structure is investigated by ab initio plane-wavepseudopotential density functional theory method, and the thermodynamicproperties of the ZB and RS structures are obtained through thequasi-harmonic Debye model. It is found that the transition from the ZBstructure to the RS structure occurs at the pressure of about 16.3,GPa,this fact is well consistent with the experimental data and other theoretical results. Thedependences of the relative volume V/V₀ on the pressure P, the Debyetemperature Th and specific heat C_V on the pressure P, as well asthe specific heat C_V on the temperature T are also obtainedsuccessfully.