Tight-Binding Theory of Manganese and Iron Oxides

TL;DR

This paper develops a tight-binding model to explain the electronic and magnetic properties of manganese and iron oxides, emphasizing the role of interorbital couplings and valence states.

Contribution

It introduces a universal tight-binding framework that accounts for electronic structure and cohesion in manganese and iron oxides, linking properties to atomic parameters.

Findings

Cohesive energies are similar across MnO, Mn2O3, and MnO2, dominated by manganese s to oxygen p transfer.

Small Coulomb shifts of d-states are observed, with minor corrections from minority-spin couplings.

Electronic and magnetic properties align with the tight-binding parameters and valence state considerations.

Abstract

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.