Particle spaces core-valence correlation

Mukherjee/91/ initially proved LCT for incomplete model spaces having n-hole n—particle determinants, showing also at the same time the validity of the core—valence separation. The corresponding open-shell perturbation theory of Brandow/20/ for such cases leads to unlinked terms and a breakdown of the core-valence separation, which used IN for O. Mukherjee emphasized that it is essential to have a valence-universal wave operator O within a Fock space formulation/91/ such that it also correlates the subduced valence sectors. Later on,... 

Although the size and complexity of the perturbation expansions increases rapidly with any further particle in either the valence or core-valence orbitals, the steps below are rather general and independent of fhe shell structure of the particular atom or molecule. In the following, therefore, we assume only that all the operators of inferesf have a represenfafion in second quanfizafion and that the matrix elements are calculated with regard to the basis function (pa) M from the model space. Then, the four sfeps below apply for bofh, fhe computation of correlation energies as well as for many ofher atomic and molecular (transition) properties ... 

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