The basic atomic processes of corrosion I. Electronic conduction in MnO, CoO and NiO

Abstract

We have used simple ionic models to study the lattice distortion and polarization about localized holes in MnO, CoO and NiO. Our results demonstrate a rather fine balance between factors favouring localized small polarons and band-state large polarons, but we find the correct trend consistent with the observation of small polarons in MnO and large polarons in CoO and NiO. Our calculations of the activation energy for hole hopping give results in good general agreement with the measured free hole mobility in MnO and the trapped small polaron motion in CoO and NiO. We can also make reasonable estimates of the binding of the hole to a monovalent dopant. These satisfactory conclusions seem to justify the neglect of the complications of Jahn-Teller, crystal field and covalency contributions in our models.