Subject: PM3tm-summary

From: "Paneth" <[email-masked]>
Date: Tue, 11 May 1999 14:35:32 +0200

I'd like to thank people who responded to my querry regarding PM3tm
parametrization. The question was: which implementation of this Hamiltonian
gives correct results (Spartan or Hyperchem)?

Some people suggested staying away from it, usage of ab initio (MINI), or
useage of at least DTF methods.

The difference between implementations in the above-mentioned programs was
pointed out: in Spartan correction for H-H repulsion is added by default in
calculations containing tms. (Unfrotunately I couldn't check if this was my
problem since the keyword turning it off does not work in PC Spartan Pro).

Finally, thanks to Alan Shusterman, we were able to compare data for CrO3.
C3v geometry gave in all versions of Spartan (unix, mac, pc) heat of
formation of -79.14 kcal/mol while Hyperchem yielded -185.5 kcal/mol
(experimental data: about -52 kcal/mol JPC 1996, 100, 6354) - geometrical
results are the same from both programs.

Piotr
******************************************************
Professor Piotr Paneth
Department of Chemistry, Technical University
Zeromskiego 116, 90-924 Lodz, Poland
phone/fax: (+48 42) 631-3199      fax: (+48 42) 636-5008