ELECTRONIC-STRUCTURE OF LA2CUO4 AND YBA2CU3O6 - A LOCAL-SPIN-DENSITY APPROXIMATION WITH ON-SITE COULOMB-U CORRELATION CALCULATIONS

The electron-electron correlation has been considered by using the local-spin-density approximation (LSDA) with on-site Couloinb interaction in the first-principles discrete variational cluster method. Based on the correction to LSDA, we have carried out self-consistent electronic-structure calculations for the strongly correlated electronic systems of La2CuO4 and YBa2Cu3O6. In contrast to LSDA, the LSDA+U calculations reveal the experimentally observed antiferromagnetic and insulating ground state. The energy gap for these compounds is of a charge-transfer character, and the values of the energy gap and Cu magnetic moment are in good agreement with experiments. The orbital character of the states near the Fermi level in La2CuO4 and YBa2Cu3O6 is discussed and a comparison with experiments is made.