Intermolecular Energy Decomposition Schemes Equivalence Between Terms

However, due to the availability of numerous techniques, it is important to point out here the differences and equivalence between schemes. To summarize, two EDA families can be applied to force field parametrization. The first EDA type of approach is labelled SAPT (Symmetry Adapted Perturbation Theory). It uses non orthogonal orbitals and recomputes the total interaction upon perturbation theory. As computations can be performed up to the Coupled-Cluster Singles Doubles (CCSD) level, SAPT can be seen as a reference method. However, due to the cost of the use of non-orthogonal molecular orbitals, pure SAPT approaches remain limited 

At this point, it is important to notice that in general, the sum of the contributions do not match exactly AE as higher order terms are present. The difference between the sum of contributions and AE is denoted 8E. Concerning the variational schemes, SE is generally small in the CSOV (or RVS) approach thanks to the antisymmetry conservation and not present in the Ziegler scheme as the Eoi term is taking into account a fully relaxed wavefunction. It is not the case for the KM scheme which 

SAPT es exch -rep indjesp exch -ind,resp resp 

---

Intermolecular Energy Decomposition Schemes Equivalence Between Terms... 

---