Correlated capped subsystem calculations as a way to include electron correlation locally: a test for substituent effects on bond energies

A new integrated technique employing the capped subsystem strategy of the IMOMO method is used as a way to include electron correlation (configuration mixing) in a molecular subsystem without requiring a transformation to localized orbitals. We obtain good results for bond energies that require a correlated treatment of at least part of the molecule, and we include the effect of substituents in any part of the molecule. An especially important result is that the method provides a convenient and practical way to include electron correlation in a localized subsystem, while retaining the quantum mechanical electronic effects of uncorrelated substituents.