RE: [AMBER] resp_problem

From: Ross Walker <ross.rosswalker.co.uk>
Date: Sat, 24 Oct 2009 15:39:01 -0700

Hi Vhakkim,

> I did calculation (metal complex) of
> partial
> charge using resp method, the following line is present in the esp.dat
> file
>
> 61*****
>
> Here 61 means number of atoms then number of esp should come but it
> shows
> ****** instead of numbers and i gave the no of esp is 107753.

Somewhere in the code there will be a format sting set to I5. This will
limit the output to 5 digit integers, hence the maximum number of ESP points
is 99,999. You have two options. The first would be to edit the code and
look for the I5 format string and change it to I6. This will have to be done
wherever this value is read or written. You would also need to check any
arrays used to read the points to make sure they are long enough.

Alternatively you could reduce the number of points generated, I assume in
Gaussian. I assume you have something like this in your Gaussian route line:

#P HF/6-31G* SCF=Tight Pop=MK IOp(6/33=2,6/41=10,6/42=17)

IOp 6/41=10 specifies that 10 concentric layers of points are used for each
atom.
IOp 6/42=17 specifies the density points in each layer - 17 gives 2500
points per atom. For larger molecules it may be necessary to reduce this
slightly.

Thus you could reduce 6/42=17 to 16 or reduce the number of layers. This
will have an effect on the results but should be minimal since this is still
a very fine grid for resp charges.

You could also try RED to do the calculation for you. See the AMBER website
for a link.

Good luck,
Ross

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|\oss Walker

| Assistant Research Professor |
| San Diego Supercomputer Center |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
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Received on Sat Oct 24 2009 - 16:00:03 PDT
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