Open-Shell Many Body Formalisms

CATEGORIZATION OF THE OPEN-SHELL MANY-BODY FORMALISMS... 

It is known that within the framework of the Roothaan coupling operator approach, there is no unique way of choosing a reference Hamiltonian, with respect to which a perturbation expansion for correlation effects can be developed. Several proposals have been made for open-shell many-body perturbation theory expansions based on a reference from the ROHE formalism [41, 42] or the umestricted Hartree-Fock formalism [43, 44]. We follow our papers [10, 45] where an alternative technique for the open-shell systems has been developed. In our method, the second-order correction to the ground state energy can be presented by [45] ... 

Beyond these simple manifestations of many-body excitations of the extended states, the strong interaction between deep holes and open and highly correlated outer shells gives rise to complex multiplet (see section 4) and satellite structure in the spectra. So far only in the simple cases of the light lanthanide soUds detailed many-body formalisms yield a lull understanding of these phenomena (see section 6). 

Mukherjee D, Moitra RK, Mukhopadhyay A. Applications of a non-perturbative many-body formalism to general open-shell atomic and molecular problems calculation of the ground and the lowest ir-ir singlet and triplet energies and the first ionization potential of trans-butadiene. Mol Phys. 1977 33 955-969. 

I. Hubac and P. Carsky, Phys. Rev., All, 2392 (1980). Correlation Energy of Open-Shell Systems. Application of the Many-Body Rayleigh-Schrodinger Perturbation Theory in the Restricted Roothaan-Hartree-Fock Formalism. 

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