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 investigate d in the crystals with compositions from the pseudobinary cut line Cu2Se-In 2Se3. This includes CuInSe2, indium-rich ternary compounds (Cu2In4Se7, CuIn 3Se5, CuIn5Se8, CuIn7Se11) and alpha -In2Se3. 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 CuInSe2 and alpha -In2Se3 for the energies up to 17 eV above the conduction band minimum by the LMTO-ASA meth od. The RSMS approach represented by the FEFF8 code is used to calculate th e 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.