Subject: Summary: Fitting point charges to ESP with Spartan

From: Bjoern Rabenstein <[email-masked]>
Date: Mon, 04 Nov 1996 15:11:56 +0100

I got many replies, of which some were already posted to the list.
Among them were also mails from Philip E. Klunzinger from Wavefunction
and even Curt Breneman himself. (:

Conclusions:
Spartan IS essentially using a CHELPG-approach, i.e. points are on a
grid and not on atom centered shells.

The slightly different results compared to stand alone CHELPG or CHELP
included in Gaussian9x could be explained by the following:
- number of used points
- default set of atomic exclusion radii
- how far away from atoms reaches region included in calculation
  (in neutral molecules charges will approach to zero if too many points
  too far away are included)
- instability of least square fitting (alternative would be singular 
  value decomposition, see posting of Konrad Hinsen)
-- 
     Bjoern Rabenstein * Freie Universitaet Berlin * Inst. f. Biochemie
 Inst. f. Kristallographie * AG Knapp * Takustrasse 6  * D-14195 Berlin
                 [Telephon] +49-30-838-3484   [Telefax] +49-30-838-3464
 [email] [email-masked]  [WWW] http://www.chemie.fu-berlin.de/~rabe/