Pressure based first-principles study of the electronic, elastic, optic and phonon properties of zincblende InN

Abstract

Generalized gradient approximation proposed by Perdew–Burke–Ernzerhof (GGA-PBE) is used to determine the effect of pressure on electronic, elastic, acoustic, optical and vibrational properties of zincblende InN along with the Ultra soft pseudopotential method. The structural properties show good consistency and stability at elevated pressures. The zincblende InN displays zero band gap and its metallicity maintains even at high pressures. The density of states appear in a quarterly divided region, where the contribution of different states have been discussed, and it is found that the peak positions are consistent with experimental L1, L3, K absorption and emission edges. The effect of pressure appears in strong hybridization due to which DOS above and below the Fermi level are shifting to the corresponding higher and lower energies due to p–d hybridization. The calculated elastic constants agree well with the literature. Except C44 and Cs, all others show an increasing trend with the pressure. Acoustic wave speeds have been calculated in [100], [110] and [111] directions with the help of elastic constants for the first time. For the optical properties, the main peaks of the imaginary part of dielectric function lie in close vicinity of experiment and shift to higher energies with a reduction in peak intensities when the pressure effects come into play. Similarly the absorption peaks are red shifted with respect to hydro-static pressure. The refractive index is maximum at lower energies and its magnitude reduces with pressure and the maximum value of energy loss function is obtained corresponding to minimum dielectric function. Phonon frequencies in high symmetry directions agree well with the only available first principle study. Except XTA, WTA, and LTA, all the other modes show an increase in phonon frequencies when pressure is exerted, this is further confirmed by Gruneisen parameters calculated for the first time.