Configuration interaction method advantages

It is well known that Hartree-Fock (HF) theory not only has been proven to be quite suitable for calculations of ground state (GS) properties of electronic systems, but has also served as a starting point to develop many-parti-cle approaches which deal with electronic correlation, like perturbation theory, configuration interaction methods and so on (see e.g., [1]). Therefore, a large number of sophisticated computational approaches have been developed for the description of the ground states based on the HF approximation. One of the most popular computational tools in quantum chemistry for GS calculations is based on the effectiveness of the HF approximation and the computational advantages of the widely used many-body Mpller-Plesset perturbation theory (MPPT) for correlation effects. We designate this scheme as HF + MPPT, here after denoted HF -f- MP2. ... 

The conceptual simplicity of the configuration interaction method is very appealing, and its variational nature is an important advantage, but its principal strength lies in its flexibility and generality. It can be applied straightforwardly to any electronic state, and can be spin- and symmetry-adapted relatively easily. 

In comparison with the more standard Configuration Interaction (Cl) method, the one-particle Green s function approach offers the essential advantages, in the outlook of numerical applications on extended systems, of a stronger and systematic compactness (30) of the configuration spaces in high order approximations and of energy separability (5,31) in the dissociation limit (size-consistency). The latter is a necessary prerequisite ( ) for a correct (i.e. size-... 

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