AMBER Archive (2006)

Subject: Re: AMBER: RESP charges of iron-porphyrin system

From: Gustavo Seabra (gustavo.seabra_at_gmail.com)
Date: Thu Oct 19 2006 - 08:40:20 CDT

To get Gaussian to generate the RESP charges you can use a route card like:

#HF/6-31G* SCF=tight Test Pop=MK iop(6/33=2) iop(6/42=6)

The HF/6-31G* is the standard method for generating RESP charges for
GAFF parameters, SCF=tight is always recommended, and Test just tells
Gaussian not to bother with job archiving.

The really important keyword here is Pop=MK, which tells Gaussian to
"Produce charges fit to the electrostatic potential at points selected
according to the Merz-Singh-Kollman scheme" [quote from G03 manual].
IOp(6/42=6) tells it to use 6 points per unit area in the RESP fit.
[IOp(6/33) is not documented, so I can't tell much without having
access to G03 source code.]

By the way, that's what you would get if you just used antechamber to
create the G03 input file:

 $ antechamber -fi pdb -i myfile.pdb -fo gcrt -o myfile.com

Or something like it, depending on the kind of files you have.

HTH,

Gustavo Seabra.

On 10/18/06, Shin Tokumoto <stokumoto_at_tara.tsukuba.ac.jp> wrote:
> Dear Amber users,
>
> Regarding RESP charge of Fe, I have a question.
>
> I would like to calculate RESP charges of iron-porphyrin system.
> First I performed Gaussian03 on this iron-porphyrin system, adding to
> the input
> file both a keyword, "pop=readradii", and the value of Fe V.D.W radius
> to get the
> electrostatic potential. By using the output file, I then performed
> antechamber and
> could get a prep file. But there was no information about the Fe RESP
> charge in this file,
> that is to say, the corresponding place is empty.
>
> Would you tell me how to get the correct RESP charge of Fe?
>
> Thanks for any help.
>
> Shin tokumoto.
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