X-ray absorption near-edge structure of selenium in the Cu-In-Se system

The x-ray absorption near edge structure (XANES) of selenium is investigated in the crystals with compositions from the pseudobinary cut line Cu 2 Se-In 2 Se 3 . This includes CuInSe 2 , indium-rich ternary compounds (Cu 2 In 4 Se 7 , CuIn 3 Se 5 , CuIn 5 Se 8 , CuIn 7 Se 11 ) and α-In 2 Se 3 . The absorption at the K and L 3 /L 2 edges of selenium has been measured using synchrotron radiation. Two theoretical approaches are used to the interpretation of the experimental data: the band structure calculation and the real-space multiple-scattering (RSMS) method. In the first one, the angular momentum projected densities of states at Se sites are calculated for CuInSe 2 and α-In 2 Se 3 for the energies up to 17 eV above the conduction band minimum by the LMTO-ASA method. The RSMS approach represented by the FEFF8 code is used to calculate the XANES spectra for the phases with tetragonal symmetry. Clusters up to 160 atoms are used in the calculations. The influence of different structural factors on the selenium XANES is studied.