Preparation, electronic structure and optical properties of Na2GeSe3 crystals

From the first principles, in the framework of the density functional theory in LDA and LDA+U approximations, the band structure, total and partial densities of electronic states, spatial distribution of the electron charge density, also the optical functions: dielectric constant, refractive and absorption indices, reflection and absorption coefficients of Na2GeSe3 crystal have been calculated. According to the calculation results, Na(2)GeSe(3 )is a direct-gap crystal with the top of valence band and the bottom of conduction band at the point Gamma of Brillouin zone. The calculated band gap is E-gd = 1.7 eV LDA and E-gd = 2.6 eV in the LDA+U approximations. Based on the data of total and partial densities of electronic states, contributions of atomic orbitals to the crystalline ones have been determined. Also, the data of chemical bond formation in the crystals under discussion have been obtained.