Ab initio study of corundum-like Me2O3oxides (Me=Ti, V, Cr, Fe, Co, Ni)

Abstract

Periodic unrestricted Hartree–Fock methods, with all-electron basis sets and aposteriori estimate of correlation energy, have been used to study the ground-state total energy of the title compounds with rhombohedral Rc corundum-type structure. Co₂O₃ and Ni₂O₃ are shown to be stable oxides with quite regular binding energies at the athermal limit. The relative stabilities of the AF1 (R3c), AF2 (R) and AF3 (R32) antiferromagnetic structures have been investigated, showing that Cr₂O₃ adopts the AF1 configuration, while Fe₂O₃, Co₂O₃ and Ni₂O₃ prefer AF2; this is accounted for in terms of σ- and π-type superexchange interactions. The spin polarization of electron transfer from O^2- to Me³⁺ has been analysed, showing that only minority-spin electrons are transferred for Me=Fe, Co and Ni, while the total transfer is doubled for the other oxides by the majority-spin contribution.