Orbital and charge ordering in Pr1-xCaxMnO3 (x=0 and 0.5) from the ab initio calculations

The electronic structure of the doped manganites Pr1-xCaxMnO3 was calculated by the LSDA + U method which takes into account the local Coulomb interaction between d electrons of transition-metal ions. In contrast to the standard local-spin-density approximation, no Jahn-Teller lattice distortions are needed to reproduce the experimentally observed orbital ordering in the undoped PrMnO3. The correct ground state, a charge and orbital ordered antiferromagnetic insulator, was obtained for Pr1/2Ca1/2MnO3. The results are in a good agreement with the neutron-diffraction data.