Electronic structure and optical properties of CdMoO4 and CdWO4

In previous work, we studied the electronic structure of several molybdate and tungstate crystals having the scheelite structure. The wolframite structure is another common form for molybdate and tungstate materials. In this paper, we compare two chemically similar materials that naturally form in the scheelite and wolframite structures-CdMoO4 and CdWO4, respectively. We compare the electronic structure and approximate optical properties of these materials within the framework of density-functional theory. One major difference between the two materials is in their lower conduction bands, which are dominated by the crystal-field-split d bands of the transition metal. For CdMoO4 the Mo ions have an approximately tetrahedral coordination causing the lower conduction band to be twofold degenerate, while for CdWO4 the W ions have an approximately octahedral coordination causing the lower conduction band to be threefold dengenerate.