Subject: Summary: optimization and point charges...

From: Artem Masunov <[email-masked]>
Date: Wed, 14 Aug 1996 17:52:51 -0400 (EDT)

Dear All,
I would like to thank Magan Govender and Sudha Srinivas for their replies,
it looks like there is no existing program to perform the geometry 
optimization in the presence of point charges; Gaussian94 needs
modification in order to read and write point charges from checkpoint
file. Kitaura-Morokuma analysis is disputable and does not let you
simulate molecule by point charges. NOSYMM is really necessary to
perform optimization in uniform electric field, but it does not help 
in the case of point charges...
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The original question was:

    To study electrostatic component of intermolecular interaction
I would like to do (partial) geometry optimization in the presence of
background point charges. Unfortunately, Gaussian94 does not have this
option. 
    Gaussian94 is not supposed to optimize in uniform electric field
also, but in fact it does. Keeping this in mind, I run optimization with
background point charges. The first step seemed to work fine, generated
new geometry and derivatives, etc. Nevertheless, at the second step point
charges disappeared and eventually the geometry converged back to where I
started. I suspect, Gaussian94 does not pass the information about 
point charges to some COMMON blocks, so they do not survive at the
following steps of optimization route.
    Is there some Gaussian94 guru who can suggest me where to look or
have alternative opinion on what is happening?
    Any opinions/pointers on geometry optimization in the presence of
background point charges will be much appreciated.

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The answers were:

Date: Mon, 05 Aug 1996 15:53:09 +0930 (SAST)
From: Magan Govender <[email-masked]>

The Morokuma Decom analysis can give you the ES component within the 
SCF interaction energy ...

Are you imposing any symmetry to the geometry that you are 
optimizing?..., you could try NOSYMM, in order to prevent this 
collapsing into the original orientation....

Date: Wed, 7 Aug 1996 12:29:15 -0500 (CDT)
From: Sudha Srinivas <[email-masked]>

    The background point charge is read in only in the first step of
a gaussian optimization run. To get around this problem, you should specify
that the background charge be read in from the checkpoint file.