Correlation of 1s binding energy with the average quantum mechanical potential at A nucleus

Changes in binding energies of 1s core electrons for C. N. O. and F atoms in different molecular environments have been studied by examination of negatives of inner-shell orbital energies ((-is an element of)Is) from ab initio "double-zeta(n) quality LCAO SCF MO wavefunctions. As contrasted with many previous correlations of binding energies with point charge models. changes of orbital energies have been related to the potential at the nucleus on which the 1s orbital sits. properly calculated as a quantum mechanical expectation value. The contribution of the 1s to the potential is insensitive to environment. and consideration focuses on the "external potential" Phi(ext) due to the remainder of the system outside of the 1s. Shifts in -is an element of(1s) are in all cases nearly the same as shifts in Phi(ext) (using atomic units). the average of eleven cases giving Delta(-is an element of 1s)/Delta(Phi(ext)) = 1.11. An analysis of the equations. based on localized valence MO's and supported by numerical examples. shows this to be a generally expected result. with some possible exceptions being outlined.