Subject: G98: pcm charge errors

From: Christoph Maerker <[email-masked]>
Date: Fri, 28 May 1999 12:34:41 +0200 (MEST)

Institut Le Bel 
Universite Louis Pasteur
Postal-Address: 4, rue Blaise Pascal, F- 67000 Strasbourg FRANCE
Phone: +33/3-88-41-53-19
Fax:   +33/3-88-60-63-83

A tous,

I do some PCM single point calculations with G98. In the output file I find
notes like the following one:

Error on NUCLEAR pol.charges = 0.80860 Error on ELECTR. pol.charges =-1.00268

An "error" of about one unit charge seems quite a lot to me. 

1) How does this error affect computed solvation (free) energies, I mean how 
reliable are these values ? 
2) Is there a rule of thumb to which magnitude errors in polarisation charges 
are acceptable ?
3) Are there keywords or keyword options by which one can reduce such
charge errors ?

By the way, I noticed that these charge errors depend on the solvation model
chosen. Empirically the COSMO implementation (i.e. cpcm) often has smaller
charge errors than dpcm, but there are exceptions too.

I will summarize to the list.

Amicalement,
Christoph