The affection of spin-orbit coupling on the electronic and optical properties of AlB2-like transition metal diborides: A first principle study

Abstract

Based on the density functional theory and using GGA and GGA + so approximations, the electronic and optical properties of bulk TMB2 (TM = Cr, Mn, and Fe) are calculated. We calculate the electronic properties of these compounds in the presence of spin-orbit interaction. The highest and lowest spin-orbit effects are observed in MnB2 and FeB2 compounds respectively; this effect also causes degeneration disappear in these compounds and its greatest effect is on the orbital p of transition metals at low energy levels. In the up spin state and near the Fermi level, the energy levels are shifted to higher energies, which is not commonly observed in down spin state. Moreover, the optical properties of TMB2 including the real and imaginary parts of ε(ω), energy loss function, absorption coefficient, reflectivity, and refraction are calculated for two directions. The spin-orbit effect has significant influence on the optical coefficient of these compounds. Energy loss of the emitted photons is significantly reduced in these compounds at both directions in the presence of spin-orbit effects. Also, the spin-orbit effect in both directions increases the plasmon frequency and eliminates the transparency of the material at higher energies than the plasmon frequency. Keywords: Transition metal diborides, Electronic properties, Optical properties, Density functional theory