LOCAL-DENSITY FUNCTIONAL AND ON-SITE CORRELATIONS - THE ELECTRONIC-STRUCTURE OF LA2CUO4 AND LACUO3

State-of-the-art electronic-structure calculations based on the local- density approximation (LDA) to the density functional fail to reproduc e the insulating antiferromagnetic ground state in the parent compound s of the high-temperature oxide superconductors. Similar problems have been observed earlier in classical transition-metal oxides such as Fe O, CoO, and NiO. In this work we present the method which delivers the correct insulating antiferromagnetic ground state in the correlated o xides preserving other properties as well as the efficiency of the sta ndard LDA. The method embeds the relevant (for a given system of elect rons) part of the Hubbard Hamiltonian into the Kohn-Sham LDA equation. The resulting Hamiltonian attempts to fix two intrinsic problems of t he LDA: the deficiency in forming localized (atomiclike) moments and t he lack of discontinuity of the effective one-particle potential when going from occupied to unoccupied states. We present the detailed stud y of La2CuO4 and LaCuO3. In the case of La2CuO4 the energy gap and the value of the localized magnetic moment in the stable insulating antif erromagnetic solution are in good agreement with experiment. We compar e our results with the standard local spin density approximation calcu lation and multiband Hubbard model calculations, as well as with resul ts of spectroscopy: inverse photoemission, valence photoemission, and x-ray absorption at the K edge of oxygen. In the case of LaCuO3 such a n extensive comparison is limited due to the limited data available fo r this compound. We discuss, however, the electric and magnetic proper ties and the insulator-metal-insulator transitions upon increase of ox ygen deficiency.