Structural and elastic stabilities of InN in both B4 and B1 phases under high pressure using density-functional perturbation theory

Structural and elastic properties of InN in both B4 (wurtzite) and B1 (rocksalt) phases are studied over a wide range of pressures from 0 to 20 GPa at T = 0 K, using the density functional perturbation theory (DFPT) for the first time. Pressure dependencies of the total energy, structure parameters, elastic stiffness constants cij, bulk modulus, Kleinman internal strain parameter, shear anisotropies and their relationship to elastic stability are also explored. In addition, the aggregate elastic modulus (B, G, E), Poisson's ratio (ν) and Lame's coefficients (λ) are estimated within the framework of Voigt-Reuss-Hill approximation for ideal polycrystalline InN aggregates, and thus the longitudinal and transverse sound velocities are obtained. We estimated the Debye temperature ΘD(T), energy E(T), entropy S(T), free energy F(T), and lattice heat capacity cv(T) as a function of temperature at null pressure for B4 (wurtzite) phase. Our results are in reasonable agreement with the available theoretical and experimental data for B4 phase. To our knowledge this is the first quantitative theoretical prediction of the B1 (rocksalt) that is still awaiting experimental confirmations.