Considerations regarding the local treatment of Laplace transform MPPT

The Laplace transform approach of Mّller-Plesset perturbation theory (MPPT) by Hنser and Almlِf has been investigated for its suitability for localized orbitals. The most critical step in this algorithm, the Laplace transformation of the localized orbitals, leads to a destruction of the physical meaningful localization. However, this downfall does not lead to a decrease of negligible LCAO coefficients in the time critical four index transformation of the electron repulsion integrals. Therefore, the use of localized orbitals or more generally the use of orbitals with a small number of significant LCAO coefficients (mathematically localized orbitals) is a useful refinement in the Laplace transform method of MPPT.