2014 Volume 13 Issue 1 Pages 32-42
The four-component relativistic general multiconfigurational quasidegenerate perturbation theory (GMC-QDPT) and its applications to some atomic and molecular systems are reviewed. An efficient and accurate approximation to the relativistic GMC-QDPT is also presented. In the approximation, the terms including core to virtual excitations in the second-order effective Hamiltonian are replaced with those of the conventional quasidegenerate perturbation theory. The approximation form, which we call semi-approximate second-order form, is applied to some molecular systems. The computed excitation energies and potential energy curves were in good agreement with the original GMC-QDPT values as well as available experimental data.
