First-principles study of pressure-induced phase transition in silicon carbide

The phase transition of SiC from the zinc blende (ZB) structure to the rocksalt (RS) structure under pressure is investigated by the first principles plane-wave pseudopotential density functional theory method. The results obtained are in good agreement with the experimentally measured data and other theoretically calculated results. It is found that the pressures of transition of SiC from the ZB structure to the RS structure are 74.6 GPa from total energy-volume data and 75.4 GPa from the enthalpy calculations. Moreover, through the quasi-harmonic Debye model, in which the phononic effects are considered, the dependences of relative volume V/V0 on pressure P at T=0, 1400 K are successfully obtained. The calculated volume reduction at the transition is 18%. In particular, from the high-pressure elastic constants obtained, the ZB structure SiC is found unstable when the applied pressure is larger than 126.6 GPa. This value is in excellent agreement with the experimental data and the molecular dynamics (MD) simulation results.