Subject: SUMARY:MP2 density in CHK file.

From: <[email-masked]>
Date: Thu, 7 Nov 1996 13:49:37 +0100

Hello,

Here is the sumary about my question to the CCL:

THE QUESTION:

I am using gaussian92 to fit atomic charges with potential
derived methods.
To save computer time the electronic density can be read
>from the checkpoint file to avoid to calculate it several time
if you want to use it for different calculations.
By default, the HF density is saved in the CHK file.
Since I want to use the MP2 density, could somebody tell me if
there is a way to save the MP2 density in the CHK file and if
so, how to do it ??
More is it possible to save both the HF and the MP2 densities in the
same CHK file??

******************************************************************

THE ANSWERS:

******************************************************************
>From Seiji Mori
e-mail: [email-masked]
****************************************

By default, even in the MP2 calculations, SCF density was shown in the
output file and
stored in chkpoint file.
To show and store MP2 density to checkpoint file, you need to add the option ,
"density=MP2" or "density=current", that is OK.

> More is it possible to save both the HF and the MP2 densities in the
> same CHK file??

Of course, you can split to two jobs (SCF and MP2 density calculations) but
I do not know .

*******************************************************************
>From Jean-Marie Teuler
e-mail: [email-masked]

In French..

Je vous reponds directement concernant votre question concernant les matrices
de densite.

En effet, par defaut c'est la matrice de densite HF qui est stockee dans le
checkpoint.
- Si vous specifiez DENSITY=MP2, ce sera la matrice MP2.
- Si vous specifiez DENSITY=ALL, les deux matrices seront stockees et vous
pourrez selectionner celle que vous voulez utiliser avec ce meme mot-cle
DENSITY.

*********************************************************************
>From Michael Schimeczek
e-mail: [email-masked]
*******************************************

first of all, I am using Gaussian94 not 92, so I'm not sure if the results
will be the same, but here we go:

First, to check if the resulting checkpoint file really contains the desired
data, use the program formchk, which resides in the gaussian executable
directory. It reads in your checkpoint file and writes a formatted
checkpointfile (name.fchk) that you can easily read.

Then, use the keyword DENSITY in the route card.
The options are: HF, MP2, ALL, CURRENT, and several others for CI etc.
Normally, the HF density will be used as default for pop analysis (and also for
writing to the checkpoint), but if you specify DENSITY=CURRENT, the density
belonging to the method you are using is taken.
Gaussian94 then writes both HF and MP2 densities to the chkfile (if you did an
MP2 calculation).

Hope this helps (and works for G92, too!)

**********************************************************************
>From Douglas J. Fox
e-mail: [email-masked]
*************************

   If you run G92 with MP2 DENSITY=3DCurrent, both the HF and MP2 density
are saved.  You can then use DENSITY=3D(CHECK,MP2) to recover the MP2
density or DENSITY=3DCHECK to get the HF density.

**********************************************************************

Thanks to all for your help.

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