Interface with the Orbital Model

Our formula for [Eq. (3.31)] proceeds from the same general approach, using (3 — y ) fro Eq. (4.21), along the lines outlined for the calcu- 

In the valence molecular calculations, the total molecular energy can be decomposed as follows  

Ecom is the energy contribution from the core orbitals. If the latter are classified according to the nuclear center on which they are located (e.g., on nucleus k), the set of core orbitals belonging to this center is c G fe. Moreover, if these core orbitals are assumed to be nonoverlapping, the core energy may be partitioned into two terms [84]  

Now we go along with an argument offered by Tmhlar et al. [84]. In the evaluation of Eq. (4.33), and consistent with the nonoverlapping core orbitals assumption, we can neglect the core-other core exchange interactions. Because the core charge densities p (r) = 2 (r) (r) are spherically symmetric about their 

In this approximation, the net effect of the core interaction energy stands for the shielding of the nuclear charges in the internuclear repulsion. 

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