ELECTRONIC, MAGNETIC AND CRYSTAL-STRUCTURE OF CR2O3 BY THEORETICAL METHODS

The periodic unrestricted Hartree-Fock method has been adopted to calc ulate the ground-state spin-polarized wave function and total energy o f rhombohedral Cr2O3 (corundum-type structure). Contracted Gaussian-ty pe functions represent the atomic orbitals of Cr and O atoms. The leas t-energy structural configuration as a function of pressure has been d erived, as well as elastic properties and equation-of-state parameters . Results agree satisfactorily with experimental data. The relative st ability of the antiferromagnetic and ferromagnetic spin arrangements i s investigated. Density of electronic states, Mulliken population data and charge and spin density maps locate Cr2O3 at the borderline betwe en Mott-Hubbard and charge-transfer insulators. Important differences appear in the covalent character of the chemical bond and in the spin polarization of the anions, when compared to Fe2O3.