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 Hueckel molecular orbital theory(IET).The electronic energy levels of the natural mineral dioptase are also investigated,in which the Cu^2+ 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)展开▼