Inverse-perovskites Sc3GaX (X = B, C, N): A comprehensive theoretical investigation at ambient and elevated pressures

Abstract

We have made a comprehensive theoretical investigation of structural, mechanical, thermophysical, electronic, optical, thermodynamical and vibrational properties of inverse-perovskites Sc3GaX (X = B, C, N) as a function of pressure using density functional theory (DFT). Pressure dependent elastic constants are studied as regards mechanical stability, ductility, machinability and anisotropy of moduli. At ambient pressure, the density of states (DOS) at Fermi level of Sc3GaB is almost twice than that of Sc3GaC or Sc3GaN. This explains the predicted superconductivity of Sc3GaB. The nature of chemical bonding is studied via charge density distribution map. Calculated phonon dispersions exhibit dynamic stability of these compounds. The temperature and pressure dependent thermodynamic properties of Sc3GaB and Sc3GaN are investigated for the first time using quasi-harmonic Debye model. Debye and melting temperatures increase with increasing pressure which indicate that our studied compounds could be used for possible devices in harsh environments. Calculated minimum thermal conductivities of the compounds are much smaller than the optimum value (1.25 Wm−1K−1) up to 20 GPa. Hence the compounds are promising TBC materials over the entire pressure range considered. Optical properties of the compounds indicated several practical usefulness including the potential to be employed as coating materials to prevent solar heating.