The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV−vis spectroscopy and the local-spin-density approximation plus the Hubbard-U(LSDA+U)method.Four absorption bands are observed at 638 nm(1.94 eV),512 nm(2.42 eV),377 nm(3.29 eV)and 248 nm(5.00 eV),which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑,O2p↓→Mn3d eg↑,Mn3d eg↑→Mn3d t2g↓and O2p↑→Mn3d t2g↓,respectively.We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7(AO7)under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9%under the irradiation of visible light for two hours.
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