Determination of the self-consistent band structure of CrCl3, CrBr3, NiCl2, and NiBr2 by the intersecting-spheres model

It has been proven previously that the intersecting-spheres model is capable of providing accurate band structures for Si and Ge. In order to compute the electronic structure of solids with a complicated unit cell, the intersecting-spheres model has been simply modified to neglect the core states in the secular equations without significant loss of accuracy. The model formulated in this way has been used to determine the self-consistent band structure of CrCl3, CrBr3, NiCl2, and NiBr2; the electronic structures of all these materials turned out to be essentially similar. For NiCl2 and NiBr2, our results were compared with existing photoemission data, and satisfactory agreement between calculated and observed structures was found. For all the crystals investigated, a comparison was also made with ultraviolet optical and thermoreflectance data; through this comparison it seems possible to attempt a unique interpretation of the observed spectra in terms of transitions occurring between the occupied halogen p bands and the unoccupied metal s and p bands.