Effective Hamiltonian for conjugated polyenes based on the ground state single-electron density matrix

A method for constructing effective Hamiltonians using the information contained in the ground state reduced single-electron density matrices for many-electron systems is proposed and applied to trans-polyacetylene oligomers C2nH2n+2 with n = 4−24. The resulting effective Hamiltonian for π electrons, expanded in the basis set of natural atomic orbitals (NAOs) with nearest neighbor transfer integrals, reproduce accurately the Hartree-Fock ground state density matrices.