In previous work, we studied the electronic structure of several molybdate
and tungstate crystals having the scheelite structure. The wolframite struc
ture is another common form for molybdate and tungstate materials. In this
paper, we compare two chemically similar materials that naturally form in t
he scheelite and wolframite structures-CdMoO4 and CdWO4, respectively. We c
ompare the electronic structure and approximate optical properties of these
materials within the framework of density-functional theory. One major dif
ference 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 causi
ng the lower conduction band to be twofold degenerate, while for CdWO4 the
W ions have an approximately octahedral coordination causing the lower cond
uction band to be threefold dengenerate.