Electronic and optical properties of NaGaS2 compound: a first principles calculations

In this paper, based on the density functional theory (DFT) and using the full-potential linearized augmented plane wave, the electronic and optical properties of the NaGaS2 have been calculated. The electronic properties show that the electron cloud density around the Ga-S bond is larger than the Na-S bond. The main states in the valence band and conduction band are related to the S-p and Ga-s and Ga-p orbitals. The NaGaS2 is a semiconductor with a direct band gap of 4.2 eV. The optical properties indicate that the static dielectric constant in the x-direction is larger than that the z-direction. The static refractive indices of the NaGaS2 compound have been obtained 1.95 and 1.92 in the x- and z-directions, respectively. The difference of the refractive index in the energy range zero to 3 eV is approximately constant and equals to 0.037. Our calculations show that the plasmon energy of the NaGaS2 is 17.64 eV and 17.14 eV in the x- and z-directions, respectively.