I recently had a look at Multiwfn, and section 4.100.8 in the manual shows how to do simple EDA as a multistep computation. The example uses multiwfn to input initial fragment wavefunctions to compute the DE_orb with Gaussian. Incidentally, this is something which is very easy to do with nwchem without using multiwfn.

I'll use NH3..BH3 as the example at RHF/6-31G*.

**Nwchem:**

1. Optimise NH3..BH3

scratch_dir /home/me/scratch Title "NH3BH3-nw" Start NH3BH3-nw charge 0 geometry noautosym noautoz units angstrom N 0.0720500 -0.00961700 -0.336156 H 0.871540 0.292859 -0.862886 H -0.685935 0.618297 -0.534511 H -0.187686 -0.922713 -0.663436 B 0.415920 -0.0366410 1.31774 H 0.709693 1.10584 1.58004 H -0.612009 -0.411733 1.83072 H 1.33214 -0.818018 1.41958 end basis "ao basis" cartesian print B library "6-31G*" H library "6-31G*" N library "6-31G*" END scf RHF nopen 0 end task scf optimize

**Energy=-82.61181818**

2. Run SE calcs on the BH3 and NH3 fragments:

scratch_dir /home/me/scratch Title "BH3-nw" Start BH3-nw charge 0 geometry noautosym noautoz units angstrom B 0.192902 -0.0151808 0.928551 H 0.486935 1.12724 1.19093 H -0.834959 -0.390362 1.44154 H 1.10930 -0.796437 1.03042 end basis "ao basis" cartesian print B library "6-31G*" H library "6-31G*" END scf RHF nopen 0vectors output bh3.movecsend task scf energy

**Energy=-26.368337779376**

and

scratch_dir /home/me/scratch Title "NH3-nw" Start NH3-nw charge 0 geometry noautosym noautoz units angstrom N -0.150737 0.0117141 -0.725185 H 0.648571 0.314333 -1.25225 H -0.908696 0.639770 -0.923690 H -0.410582 -0.901249 -1.05260 end basis "ao basis" cartesian print N library "6-31G*" H library "6-31G*" END scf RHF nopen 0vectors output nh3.movecsend task scf energy

**Energy=-56.184296916045**

3. Finally, use the two movecs created in step 2:

4. Parse the output from step 4:scratch_dir /home/andy/scratch Title "NH3BH3-nw" Start NH3BH3-nw charge 0 geometry noautosym noautoz units angstrom N 0.0720500 -0.00961700 -0.336156 H 0.871540 0.292859 -0.862886 H -0.685935 0.618297 -0.534511 H -0.187686 -0.922713 -0.663436 B 0.415920 -0.0366410 1.31774 H 0.709693 1.10584 1.58004 H -0.612009 -0.411733 1.83072 H 1.33214 -0.818018 1.41958 end basis "ao basis" cartesian print B library "6-31G*" H library "6-31G*" N library "6-31G*" END scf RHF nopen 0vectors fragment nh3.movecs bh3.movecs output nh3bh3.movecsend task scf

So, according to the Multiwfn Manual at 4.100.8, using the values from above:iter energy gnorm gmax time ----- ------------------- --------- --------- --------1 -82.5357150919 7.36D-01 2.88D-01 0.12 -82.6078664771 2.30D-01 5.23D-02 0.1 3 -82.6117699706 2.03D-02 7.47D-03 0.1 4 -82.6118181287 2.23D-04 5.79D-05 0.1 5 -82.6118181326 2.51D-06 7.28D-07 0.1 Final RHF results ------------------Total SCF energy = -82.611818132574One-electron energy = -190.292457149391 Two-electron energy = 67.248334359392 Nuclear repulsion energy = 40.432304657425 Time for solution = 0.1s

DEtot=-82.61181818-(-26.368337779376-56.184296916045)= -37 kcal/mol (-155 kJ/mol)

DEorb=-82.611818132574-(-82.5357150919)= -48 kcal/mol (-200 kJ/mol)

DEsteric=DEtot-DEorb= 11 kcal/mol (45 kJ/mol)

This is essentially the Kitaura-Morokuma method.

See e.g. Frenking et al.in Energy Decomposition Analysis on page 44. Eq 2 defines Eint in the same way DEtot is defined above, and Eq 7 is the same Eorb as here.

DEstruc here is then DEelstat + DEPauli.

How to resolve these two factors from one another, is a problem for another day.

You can also run the calcs using a single input file:

scratch_dir /home/me/scratch Title "NH3BH3-nw-eda" Start NH3BH3-nw-eda echo charge 0 geometry molecule noautosym noautoz units angstrom N -0.150737 0.0117141 -0.725185 H 0.648571 0.314333 -1.25225 H -0.908696 0.639770 -0.923690 H -0.410582 -0.901249 -1.05260 B 0.192902 -0.0151808 0.928551 H 0.486935 1.12724 1.19093 H -0.834959 -0.390362 1.44154 H 1.10930 -0.796437 1.03042 end geometry ammonia noautosym noautoz units angstrom N -0.150737 0.0117141 -0.725185 H 0.648571 0.314333 -1.25225 H -0.908696 0.639770 -0.923690 H -0.410582 -0.901249 -1.05260 end geometry borohydride noautosym noautoz units angstrom B 0.192902 -0.0151808 0.928551 H 0.486935 1.12724 1.19093 H -0.834959 -0.390362 1.44154 H 1.10930 -0.796437 1.03042 end basis "ao basis" cartesian print N library "6-31G*" B library "6-31G*" H library "6-31G*" END set geometry ammonia scf vectors output ammonia.movecs end task scf set geometry borohydride scf vectors output borohydride.movecs end task scf set geometry molecule scf vectors input fragment ammonia.movecs borohydride.movecs output molecule.movecs end task scf