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 O2- 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.