The implementation of DEDA

The implementation of DEDA represents a critical difference from other EDA methods in that energies of all intermediate states are variationally determined, which to the best of our knowledge has not been achieved before. For the frozen density energy, the optimization is done through a constrained search formulation in DFT, i.e., [/o + = min E [p], and implemented with the Wu- 

DEDA of the intermolecular interactions therefore involves four steps of variational calculations, all of which can be done with an in-house modified version of NWChem [43], As illustrated in Fig. 4.1, these four steps are (1) regular DFT calculations of the fragments (using all the basis functions in the complex), (2) a WY calculation for the frozen density of the complex that is built from the sum of fragments densities, (3) a constrained DFT calculation where charges are constrained to be the same as in the frozen density, and (4) a regular DFT calculation of the complex. 

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