The transferability of molecular fragment canonical orbitals

摘要: The ability of certain canonical orbitals isolated molecular fragments to transfer largely unchanged the environment is examined. separation fragment from total electronic problem compared with more familiar separations atomic core and localized orbitals. specific example carbonyl functional group in formaldehyde examined detail. These studies lead a new concept valence electron only calculations which electrons are assumed move an effective field provided by frozen cores. In addition, for case orbital transfer, perturbation theory analysis found be efficient method assessing quality approximate wavefunction, thus eliminating much uncertainty as systems studied. methods developed course these offer practical advantages construction wavefunctions large molecules. details application concepts existing orbtial also presented.