Theoretical study of the magnetic interaction for M-O-M type metal oxides. Comparison of broken-symmetry approaches

The unrestricted Hartree-Fock (UHF) and hybrid-density functional theory (DFT) calculations have been carried out for the metal oxides such as copper oxides and nickel oxides. In order to elucidate magnetic properties of the species, the effective exchange integrals (J(ab)) have been obtained by the total energy difference between the highest and lowest spin states in several computational schemes with and without spin projection. The mixing ratios of the exchange correlation functionals in the hybrid DFT method have bem reoptimized so as to reproduce the J(ab) values for strongly correlated oxides. The natural orbital analysis has also been performed for elucidation of symmetry and occupation numbers of the magnetic orbitals. From these calculated results, we discuss characteristics of the magnetic interactions for metal oxides in the strong correlation regime. (C) 2001 Elsevier Science Ltd. All rights reserved.