Subject: Solvated TS Searches

From: "Phil Hultin" <hultin$at$cc.UManitoba.CA>
Date: Thu, 4 Dec 2003 09:13:36 -0600

I am interested in the comments about seeking solvated Transition
Structures.

We recently completed a study of SN2 displacements in sugar analogues using
B3LYP and both Onsager and IPCM solvation - the manuscripts are under review
now for J Phys Chem A (the story of this research project is a very long and
convoluted one and I won't get into it here).

However, we did not have any particular difficulty in locating first-order
saddle points using Onsager solvation.  We did this work with Gaussian 98,
which meant that we could not do geometry optimizations using IPCM (and the
SC-IPCM didn't work).  We simply took "gas phase" structures as starting
points, and ran either Opt=TS or QST3 calculations from there using the
Onsager solvation model.  We then did single-point energy calculations using
IPCM solvation at the Onsager geometries, assuming that the actual
geometries would not be greatly different even though the energies would.

The results we obtained using this approach seemed to us to be quite in line
with expectations.

I would be very interested in hearing how others have fared using IPCM,
SC-IPCM or other higher-order continuum solvation models for geometry
optimizations with Gaussian 03.
Dr. Philip G. Hultin
Associate Department Head and
Associate Professor of Chemistry
University of Manitoba
Winnipeg, MB, Canada R3T 2N2
(vox) 204-474-9814
(fax) 204-474-7608
mailto:hultin$at$cc.umanitoba.ca
http://www.umanitoba.ca/chemistry/