Electronic structures of square planar coordinated transition metal ions in compounds with gillespite structure

Abstract

Electronic structures of square planar coordinated transition metal ions in BaCuSi4O10 and CaCrSi4O10 are investigated using the ligand-field theory (LFT), angular overlap model (AOM) and iterative extended Huckel molecular orbital theory (IET). The electronic energy levels of the natural mineral dioptase are also investigated, in which the Cu2+ ions occupy the sites of pseudo D4h symmetry. Both LFT and AOM predict that the crystal-field levels of transition metal ions in these compounds follow such an order that E (2B1g <E(2B2g <E(2A1g )<E(2Eg ), and the frequencies of the crystal-field transitions obtained from point charge calculations are in good agreement with those observed. However, the energy-level order cannot be determined unambiguously from the IET calculation because it depends on the values of parameters chosen for the calculation.