Calculated effective Hamiltonian forLa2CuO4and solution in the impurity Anderson approximation

We report local-density-functional calculations of hybridization matrix elements and effective electron-electron interactions in ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ defining a general effective Hamiltonian that we propose as an appropriate starting point for many-body calculations in this material. The parameter values lend support to an Anderson lattice model. We find the impurity approximation to this model yields a magnetic ground state of $x^2-y^2$ symmetry, a 1-2-eV insulating gap bounded by ionization and affinity levels of the same symmetry, and a calculated $d$ spectral weight in qualitative agreement with photoemission experiments. We discuss anticipated modification of these results by lattice effects.