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. [ABSTRACT FROM AUTHOR]