You may directly contact Peifeng Su, he has modified version of GAMESS-US to realize this calculation.

 Mr. Zhang,

The results are obtained using Gamess-US. Same can be obtained using Gaussian. The outputs are almost identical....but almost.

 Dr Ivanova, Do  you mean use NBO in Gaussian ?

Mr. Zhang,

I do not mean NBO, but CASSCF-6-31G-PCM.

The DGTOT in EDA-PCM in ref. J. Chem. Phys. 2012, 137, 034111 corresponds to the   interaction energy DGsol in the classical PCM.

In Table 1 (ref. J. Chem. Phys. 2012, 137, 034111) for NaCl there has been shown DETOT = -36.57 kcal.mol-1. With Gaussian I have obtained DGTOT = -38.10 kcal.mol-1 (Free Gibbs energy in solution -389928.3617 kcal.mol-1). 

You should keep in mind that in discussed reference there have not been given geometry parameters (distance, dor example) of Na+...Cl-, so that there can be error contribution due to different distances between the ions.  

Interesting, however, I don't think CASSCF will give you the break down of binding energy parameters like EDA does which is what I need. 

Mr. Zhang,

Your comment indicates that, you have not properly understood the work, which you have cited (The Journal of Chemical Physics 137, 034111 (2012); doi: 10.1063/1.4736533), in general context. In addition you do not understand CASSCF approach (an example of decomposition analysis by CASSCF is shown at the end).

The DGTOT (equation (22)) represents the total interaction energy. The DGTOT (EDA-PCM) does not represent neither binding energy nor the total free Gibbs energy in solution.

It has been given with:

DGTOT = DGele + DGex + DGrep + DGpol +DGdisp + DGdesol.

If you would like to study the binding energy between a solute and solvent molecules from the first shall, for example, using the so-called mixed solvation approach (analyte.solvent molecule in continuum) you rather need the energy change from gas-phase to solution assuming that you have binding interaction between the solute and a solvent (or more than 1 molecules) molecule. The latter value is obtained directly using Gamess-US. Your computations should include data about the isolated analyte in solution and the analyte.solvent super molecule in solution.

An example is the discussed NaCl (below). It is given NaCl in continuum. Using the mixed solvation approach you need to compute NaCl.CH3OH in continuum, for example, or any other solveln molecule of interest.

In addition, 'EDA' does not mean binding energy.

You could pay attention to the following works, dealing with classical PCM (equation (1) in the work mentioned above, in particullar, what means DGele, DGnon-ele and DGcav and how the authors have presented these terms; Refs. 1 and 2?).

Than you should compare the pairs equations (1)/(22) and corresponding pairs equations to each of the energy terms, for example, equations (2) and (29) dealing with the electronic energy (DGele). You should bear in mind that equation (2) in the classical PCM has the major contribution to the total interaction energy and the energy change from the gas - phase to solvent. This is well shown in the example below as well.

Thus subsequently you could compare terms-by-terms classical PCM and EDA-PCM in the work under discussion. In addition you should compare the first part of the shown output (below) and the equations (2) and (29).

Ref. 1 S. Miertus, E. Scrocco, J. Tomasi, Chem. Phys. 55 (1981) 117;

Ref. 2 J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 105 (2005) 2999.

In additiob you can compare the data at the end of the posting (CASSCF-PCM) for NaCl. As you can see the value DGsol is very close to the shown in Table 1 (DGTOT = -36.57 kcal.mol-1). The other terms are also shown.

Example of Gamess-US output (Energetics of NaCl in solution):

FREE ENERGY IN SOLVENT = = -621.4327856960 A.U.

INTERNAL ENERGY IN SOLVENT = = -621.3937164897 A.U.

DELTA INTERNAL ENERGY = = 0.0000000000 A.U.

ELECTROSTATIC INTERACTION = -0.0390692063 A.U.

PIEROTTI CAVITATION ENERGY = 0.0000000000 A.U.

DISPERSION FREE ENERGY = 0.0000000000 A.U.

REPULSION FREE ENERGY = 0.0000000000 A.U.

TOTAL INTERACTION (DELTA + ES + CAV + DISP + REP) = -0.0390692063 A.U.

TOTAL FREE ENERGY IN SOLVENT = -621.4327856960 A.U.

FREE ENERGY IN SOLVENT = -389955.00 KCAL/MOL

INTERNAL ENERGY IN SOLVENT = -389930.49 KCAL/MOL

DELTA INTERNAL ENERGY = 0.00 KCAL/MOL

ELECTROSTATIC INTERACTION = -24.52 KCAL/MOL

PIEROTTI CAVITATION ENERGY = 0.00 KCAL/MOL

DISPERSION FREE ENERGY = 0.00 KCAL/MOL

REPULSION FREE ENERGY = 0.00 KCAL/MOL

TOTAL INTERACTION = -24.52 KCAL/MOL

TOTAL FREE ENERGY IN SOLVENT = -389955.00 KCAL/MOL

----- ENERGY CHANGE FROM GAS PHASE TO SOLVENT -----

ELEC ELEC+CAV ELEC+CAV+DIS+REP

-22.576 -22.576 -22.576 KCAL/MOL

NaCl-Methanol/CASSCF-PCM (Gaussian):

(a.u.) = -621.389877

(a.u.) = -621.446268

(a.u.) = -621.450069

(a.u.) = -621.385766

(a.u.) = -621.450595

Total free energy in sol.

(with non electrost.terms) (a.u.) = -621.444622

(Unpol.Solute)-Solvent (kcal/mol) = -35.39

(Polar.Solute)-Solvent (kcal/mol) = -40.68

Solute Polarization (kcal/mol) = 2.58

Total Electrostatic (kcal/mol) = -38.10

Cavitation energy (kcal/mol) = 8.47

Dispersion energy (kcal/mol) = -5.35

Repulsion energy (kcal/mol) = 0.63

Total non electr. (kcal/mol) = 3.75

DeltaG (solv) (kcal/mol) = -34.35

Dear Dr Ivanova.

You are absolutely correct on the binding energy and the interaction energy. I definitely misused them.

Could you please provide me with the instruction on how to run CASSCF-PCM calculations? I think it will be a very useful knowledge to obtain - Thank you very much.

P.S. Can CASSCF-PCM calculate the interaction energy of two monomers of a covalent bonded molecule in PCM solvent?