| We study charge, orbital and magnetic order using the effective model on the 8x8 La2-xSrx Ni O4 cluster composed out of only Ni sites renormalized by surrouding oxygens. At each site we consider Wannier orbitals of the eg character. The model Hamiltonian takes into account kinetic energy, on-site Coulomb repulsion, Hunds exchange, spin-spin interaction and Jahn-Teller modes. In first step calculations within single-determinant Hartree-Fock were performed to determine the ground state wave function. In the next step the HF wave function was modified to include electron correlations by using a variant of Local Ansatz. |
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