Subject: re:heats of formation

From: "Mary O'Connor" <[email-masked]>
Date: Tue, 01 Aug 2000 16:11:34 -0400

Hello Gary and all CCLers:
           I tried doing ab initio heats of formation using HyperChem,
and spoke to their support group. The HyperChem group told me that their
software does not calculate ab initio heats of formation. Even by
analyzing the vibrations, you cannot get a read out of the proper
parameters to obtain the heat of formation. Gaussian does give a read
out of these parameters. I'd be more specific, but I don't currently
have a copy of the Gaussian manual, which can be purchased separately
from the package.
             This has been my experience with ab initio heats of
formation using HyperChem; others may be able to help you more. You
might call the HyperChem support group to see if you can modify the
calculate heat of formation script to constrain the geometry you get
using  ab initio method and apply either the AM1 or PM3 semi-empirical
methods.
         My experience with using STO-3G for a geometry optimization of
a molecule is that it gave me a much different structure than a STO
6-31G*.
          I am also a computational newbie, so please take my well-meant
observations with as many grains of salt as you feel are appropriate!

Best wishes;

Mary O'Connor
Rutgers University
New Brunswick, NJ