Allowance for polarization of atomic electron shells in MO LCAO calculations

The application of MO LCAO methods to molecules containing elements in the higher periods is discussed, especially compounds containing two phenyl rings linked via an oxygen atom. The calculated -electron density is found to agree with the observed electronic absorption spectra, dipole moment, effects of polarity on reactivity, and so on, provided that the wave function used for the heteroatom with n>2 is =c₁ npz+ +c_{2 nd}+...; the terms c_{2 nd}... provide correction for the change in the atomic function _npz produced by the surrounding atoms. This effect is not important for O, N, and C (first period). The effects of surrounding atoms on _npz for the halogen atom have evidently to be considered in computations on the -electron density for any molecule containing such an atom.