ELECTRON PAIRING AND CHEMICAL-BONDS - PHYSICAL MEANING OF EFFECTIVE PAIRS

The physical meaning of the so-called effective pairs which have been introduced recently within the formalism of pair population analysis i s discussed using the analysis of conditional probabilities of electro n density distribution for electron 1 with the reference electron fixe d in a certain point 2. It is demonstrated that from the point of view of the mutual coupling of electron motions, the effective pairs behav e analogously to singlet pairs. Based on this finding, effective pairs can be interpreted as the fraction of singlet pairs that is directly involved in bonding.