DEDA vs. EDA

The most important distinction between DEDA and other wave function-based EDA approaches [4-15] lies in the calculation of the frozen density energy. We have explained above how DEDA uses constrained search to variationally calculate the energy of the frozen density state where fragments densities are superimposed without distortions. This approach not only yields an optimal 

AFfrz separated from the density relaxation terms (AEpoi and AEct) but also allows a clean separation of electrostatic and Pauli repulsion terms. Similar intermediate states in wave function-based EDA approaches are represented by the HL antisymmetrization of two fragments wave functions, [which is] necessary because molecular orbitals from different fragments are not orthogonal. This antisymmetrized wave function, however, deforms the frozen density [12] that is to say, its density does not correspond to the sum of fragments densities. Such ambiguity makes it difficult to separate electrostatic and Pauli repulsion terms in other EDA approaches. In addition, a one-step antisymmetrization of the wave functions means its energy is not variational. 

Another unique feature of DEDA [38] is about its calculation of the charge transfer component (Afct)/ which is also calculated variationally based on the net electron flow in real space. This net counting matches classical view of charge transfer more closely and a real space approach leads to a small basis set dependency. Force field development can benefit from these unique features, as each interaction component in DEDA according to the definitions is more consistent with the typical physical picture employed in the classical force field description of intermolecular interactions. 

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