Hybrid LDA and generalized tight-binding method for electronic structure calculations of strongly correlated electron systems

A hybrid scheme for the electronic structure calculations of strongly correlated electron systems is proposed. The ab initio local density approximation calculation is used to construct the Wannier functions and obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within multiband Hubbard model is calculated by the generalized tight-binding method, which combines the exact diagonalization of the model Hamiltonian for a small cluster (unit cell) with perturbation treatment of the intercluster hopping and interactions. For undoped La2CuO4 and Nd2CuO4 this scheme results in charge transfer insulators with correct values of gaps and dispersions of bands in agreement with the angle-resolved photoemission data.