| Abstract: | The convergence of multiconfigurational many-body perturbation theory (MC MBPT ) is discussed in connection with the intruder state. Its convergence properties are first examined with a fictitious three-level system employing a Hermitian version of MC MBPT , which permits a general model space. It is then applied to the H2—H2 and N2 systems. The results suggest that a more extensive model space is likely to embrace new intruder states and the space extension be executed with due caution. |
