  The electronic structure is found to be understandable in terms of free-atom
term values and universal interorbital coupling parameters, since
self-consistent tight-binding calculations indicate that Coulomb shifts of the
d-state energies are small. Special-point averages over the bands are seen to
be equivalent to treatment of local octahedral clusters. The cohesive energy
per manganese for MnO, Mn2O3, and MnO2, in which manganese exists in valence
states Mn2+, Mn3+, and Mn4+, is very nearly the same and dominated by the
transfer of manganese s electrons to oxygen p states. There are small
corrections, one eV per Mn in all cases, from couplings of minority-spin
states. Transferring one majority-spin electron from an upper cluster state to
a nonbonding oxygen state adds 1.67 eV to the cohesion for Mn2O3, and two
transfers adds twice that for MnO2 . The electronic and magnetic properties are
consistent with this description and appear to be understandable in terms of
the same parameters.
