6.6 Energy Decomposition Analysis (EDA)

The interaction energy between molecules can be calculated with the supermolecular approach: one performs calculations for the supersystem and for the subsystems with size-consistent methods and derive the interaction energy ΔE by taking the energy difference. The energy decomposition analysis (EDA) allow a partitioning of the Hartree-Fock (HF) or DFT interaction energy in physically meaningful contributions: the classical electrostatic interaction ΔEele, the exchange-repulsion ΔEexrep, the orbital relaxation energy ΔEorb and additionally for DFT the correlation interaction ΔEcor:

 ΔEHF   =   ΔEele + ΔEexrep + ΔEorb  ,                (6.11)

ΔEDFT   =   ΔEele + ΔEexrep + ΔEorb + ΔEcor.          (6.12)
Further details and derivations of the different energy contributions can be found in [94].

6.6.1 How to perform

The EDA scheme is implemented in the module ridft and can be done with RI-Hartree-Fock and with all local, gradient corrected, hybrid and meta density functionals (please note that the functionals included in the XCFun library are not supported!).

                  ----------------------------------------------------  
                 | * Total Interaction energy  =      -0.0058700698  |  
                  ----------------------------------------------------  
                 : * Electrostatic Interaction =      -0.0134898233  :  
                 :             Nuc---Nuc       =      18.2843363825  :  
                 :             1-electron      =     -36.5372802833  :  
                 :             2-electron      =      18.2394540775  :  
                 : * Exchange-Repulsion        =       0.0112325934  :  
                 :             Exchange Int.   =      -0.0139477002  :  
                 :             Repulsion       =       0.0251802936  :  
                 : * Orbital Relaxation        =      -0.0036128399  :  
                 .....................................................