Chan, RGulacsi, Miklos2015-12-130950-0839http://hdl.handle.net/1885/91882An effective Hamiltonian for the two-band Hubbard model was derived by a canonical transformation which was calculated and summed up to infinite order. The transformed Hamiltonian contains terms with strongly renormalized interaction energies. These new interaction energies show sign reversals as a function of the hopping integral in addition to a strong reduction in the charge-transfer gap and a significant increase in the attractive oxygen Hubbard term.Keywords: Calculations; Copper oxides; Hamiltonians; Mathematical models; Mathematical transformations; Oxide superconductors; Charge-transfer gap; Infinite order; Two-band Hubbard model; Perturbation techniques200210.1080/09500830210000366702015-12-12