Mixing of Non-Degenerate Orbitals— Second-Order Perturbations

2 Mixing of Non-Degenerate Orbitals—Second-Order Perturbations 

As always, the two-center, two-electron interaction is stabilizing. Assuming the two electrons began in the lower energy starting orbital, the stabilization is as given in Eq. 14.60. 

The non-degenerate, two-orbital mixing diagram. We show the fragments as p orbitals, but they could be any type of AO or MO. 

CHAPTER 14 ADVANCED CONCEPTS IN ELECTRONIC STRUCTURE THEORY 

This is a second-order perturbation because of the square in the numerator, and typically second-order orbital interactions are smaller than those between degenerate orbitals. In the situation where overlap is neglected, we have Equation 14.61. 

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