Subject: Gaussian: recalculating thermochem

From: Jeremy Greenwood <[email-masked]>
Date: Thu, 26 Oct 2000 19:07:54 +0200

Gaussian allows the rapid recalculation of thermochemical data 
(e.g. with new scaling factor, temp., pressure) from the checkpoint 
file after a frequency job using freq=readfc

However, if the checkpoint file is missing, it gets more tricky.
We would like to recalculate the thermochemistry without having
to resort to re-running the frequency job.

A checkpoint file can be created by a single point calculation.
The force constants are listed in the archive, and can be read in 
using opt=fccards, or by editing the formatted checkpoint file by 
hand and unformatting, but this doesn't seem sufficient to 
convince Gaussian to perform freq=readfc.

One could use the information in the output file to recalculate 
the thermochemistry from first principles, but this is a little
laborious. It would be nice to have an automated procedure.

Does someone have a good way to do this?

Thanks in advance,

Jeremy
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Jeremy Greenwood                                 [email-masked]
Department of Medicinal Chemistry                      ph +45 35306117
Royal Danish School of Pharmacy                        fx +45 35306040
Universitetsparken 2, DK-2100 Copenhagen, Denmark
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On two occasions I have been asked [by members of Parliament!], 'Pray,
Mr. Babbage, if you put into the machine wrong figures, will the right
answers come out?'  I am not able rightly to apprehend the kind of
confusion of ideas that could provoke such a question. 
                                                    -- Charles Babbage
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