Phase transitions and elastic anisotropies of SiC polymorphs under high pressure

The structures, equations of state, phase transitions, mechanical stability, and elastic anisotropies of five SiC polymorphs (wurtzite, 4H, 6H, zinc blende, and rocksalt phases) under pressure were investigated based on first-principles calculations. The optimal structural parameters, densities, and volumes of the five SiC polymorphs under zero and high pressure were obtained and analyzed. The pressures of the phase and stability–instability transitions were predicted using the minimum energy principle and improved Born mechanical stability criteria, respectively, and a new phase transition criterion was developed. The elastic anisotropies of SiC under zero and high pressure were systematically discussed, and the negative Poisson's ratio of zinc blende SiC was verified.