From owner-chemistry@ccl.net Tue Jan  2 07:16:01 2007
From: "Barbara Jagoda-Cwiklik barbara.cwiklik{:}uochb.cas.cz" <owner-chemistry * server.ccl.net>
To: CCL
Subject: CCL:G: Gaussian 03 and interaction energy
Message-Id: <-33320-070102071328-4900-434RaM2qmPPcJqY5UxkYmA * server.ccl.net>
X-Original-From: "Barbara Jagoda-Cwiklik" <barbara.cwiklik##uochb.cas.cz>
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Date: Tue, 2 Jan 2007 12:15:27 +0100 (CET)
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Sent to CCL by: "Barbara Jagoda-Cwiklik" [barbara.cwiklik*uochb.cas.cz]
> Sent to CCL by: "Radoslaw  Kaminski" [rkaminski(_)acid.ch.pw.edu.pl]
>
> I would like to ask about a calculation of interaction energy using
> Gaussian 03 using supermolecular method. I'm not sure what energies from
> Gaussian output should I take to calculate an interaction energy. In
> output I have for example:
>
> .
> HarFok:  IExCor= 402 AccDes= 0.00D+00 IRadAn=         4 IDoV=1
> ScaDFX=  1.000000  1.000000  1.000000  1.000000
> Integral accuracy reduced to 1.0D-05 until final iterations.
> Initial convergence to 1.0D-05 achieved.  Increase integral accuracy.
> SCF Done:  E(RB+HF-LYP) =  -837.559949455     A.U. after    9 cycles
> .
> Counterpoise: doing DCBS calculation for fragment   1
> SCF Done:  E(RB+HF-LYP) =  -418.777857387     A.U. after    8 cycles
> .
> Counterpoise: doing DCBS calculation for fragment   2
> SCF Done:  E(RB+HF-LYP) =  -418.777180387     A.U. after    8 cycles
> .
> Counterpoise: doing MCBS calculation for fragment   1
> SCF Done:  E(RB+HF-LYP) =  -418.776871368     A.U. after    9 cycles
> .
> Counterpoise: doing MCBS calculation for fragment   2
> SCF Done:  E(RB+HF-LYP) =  -418.776965677     A.U. after    9 cycles
> .
> Counterpoise: corrected energy =    -837.558748726147
> Counterpoise: BSSE energy =       0.001200729070
> .
>
> In this case there was a job using B3LYP functional.
>
> I would be very pleased if someone tell me what values from above I should
> take, because in literature is a chaos on what to take to calculate an
> interaction energy.


Hi/czesc Radoslaw,

It was disscused here, but since I cannot find a proper link I'd try to
write it myself:

According to D.C.Young "Computational Chemistry":
E_interaction = E_AB,bAB - E_A,bAB - E_B,bAB,
where:
E_AB,bAB - E of AB complex in AB basis set
E_A,bAB  - E of monomer A in AB basis set
E_B,bAB  - E of monomer B in AB basis set

However, Gaussian in Counterpoise output presents the energies in the
following order:
E_AB,bAB
E_A,bAB
E_B,bAB
E_A  - E of monomer A in A basis set
E_B  - E of monomer B in B basis set
and in the end: corrected energy (E_corrected) & BSSE energy.

Using above output you can also calculate interaction energy this way:
E_interaction = E_corrected - (E_A + E_B)

I hope it would help :)
Best,
Basia

PS. I was really trying to resist writing: "there is no chaos" but maybe
we are thinking about two different things...


-- 
Barbara Jagoda-Cwiklik, Ph.D
Center for Biomolecules and Complex Molecular Systems
Institute of Organic Chemistry and Biochemistry,
Academy of Sciences of the Czech Republic
Prague, Czech Republic
e-mail: barbara.cwiklik,+,uochb.cas.cz