A comparative study for structural and electronic properties of single-crystal ScN

A comparative study by FP-LAPW calculations based on DFT within LDA, PBE-GGA, EV(ex)-PW(co)-GGA, and EV(ex)-GGA-LDA(co), schemes is introduced for the structural and electronic properties of ScN in RS, ZB, WZ, and CsCI phases. According to all approximations used in this work, the RS phase is the stable ground state structure and makes a transition to CsCI phase at high transition pressure. While PBE-GGA and EV(ex)-PW(co)-GGA's have provided better structural features such as equilibrium lattice constant and bulk modulus, only EV(ex)-PW(co)-GGA and EV(ex)-GGA-LDA(co)'s have given the non zero, positive indirect energy gap for RS-ScN, comparable with the experimental ones. The indirect band gap of ScN in AS phase is enlarged to the corresponding measured value by EV(ex)-PW(co)-GGA+U(SIC) calculations in which the Coulomb self and exchange-correlation interactions of the localized d-orbitals of Sc have been corrected by the potential parameter of U. The EV(ex)-PW(co)-GGA calculations have also provided good results for the structural and electronic features of ScN in ZB, WZ, and CsCI phases comparable with the theoretical data available in the literature. EV(ex)-PW(co)-GGA and EV(ex)-PW(co)-GGA+U(SIC) schemes are considered to be the best ones among the others when the structural and electronic features of ScN are aimed to be calculated by the same exchange-correlation energy approximations.