On the non-orthogonality problem in the semi-empirical MO-LCAO method

• DOI: 10.1007/bf02727554
• Publication Date: 2008-03-17T18:27:42Z
• Authors: G. Del Re
• Keywords: Orthogonality

An explicit correlation between semi-empirical MO-LCAO calculations forπ-systems including and not including overlap is derived and discussed under the assumption that overlap integrals, when taken into account, are proportional to the corresponding bond integrals. It is shown that, so far as atomic charges are concerned, the introduction of overlap makes practically no difference in the results. On the contrary all other quantities undergo sometimes serious changes. This is shown by means of a few numerical examples; it gives some support to the idea that the practice of neglecting overlap may not be so sound as has been believed.