SEARCH Articles Figures Tables Approximations order Born approximation, zeroth-order Hamiltonian Zeroth-order regular approximation Hamiltonians zeroth-order regular approximation Hartree-Fock approximation zeroth-order Hamiltonian Wave functions, approximate correct zeroth-order Zeroth order regular approximation for relativistic effects Zeroth-order Zeroth-order approximation calculation Zeroth-order approximation states Zeroth-order approximations construction Zeroth-order polarization propagator approximation Zeroth-order regular approximation Zeroth-order regular approximation (ZORA Zeroth-order regular approximation Hamiltonian/method Zeroth-order regular approximation energies/results Zeroth-order regular approximation method