Transition phase and thermodynamic properties of GaN via first-principles calculations

The transition phase of GaN from zincblende (ZB) structure to rocksalt structure (RS) is investigated by ab initio plane-wave pseudopotential density functional theory method, and the thermodynamic properties of the ZB and RS structures are obtained through the quasi-harmonic Debye model. We find that the transition phase from the ZB structure to the RS structure occurs at the pressure of 42.2GPa, which is in good agreement with other calculated values. Moreover, the dependences of the relative volume V/V0 on the pressure P, the Debye temperature Θ and heat capacity CV on the pressure P, as well as the heat capacity CV on the temperature T are also successfully obtained.