Absorption spectrum of manganian andalusite: Cluster calculation by an ab initio method

The ground state and the first few excited states of an MnO 6 9− cluster are calculated in the unrestricted Hartree–Fock model. The state ordering is 5 B 1 g , 5 A 1 g , 5 B 2 g , and 5 E g as can be expected from simpler models. Consistent with the results by the same method for copper complexes, we obtain d – d transition energies about one half or less of the experimental energies. The charge transfer spectrum is subject to a large spin polarization in the sense that the lowest charge transfer state ( 5 E u ) has five unpaired spins on Mn.