Calculating overtone energies of alkanes with ONIOM

PHYS 456

Blythe M. Ashcraft, blythe.ashcraft@srs.gov, Hydrogen Technology Research Laboratory, Savannah River National Laboratory, Aiken, SC 30809 and Robert L. Swofford, swofford@wfu.edu, Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109.
We measure vibrational overtone energies of alkanes using photoacoustic spectroscopy. The simple spectra are explained by the Local Mode Model of loosely-coupled C-H oscillators. We have used computational models which include electron correlation to describe the potential energy surfaces near dissociation. Such methods scale poorly, and calculations for alkanes larger than C5 are very expensive. Instead, we have applied the ONIOM method of Morokuma as implemented in Gaussian '03. Results will be shown where the high-level ONIOM calculation is used in the local mode region of interest and a lower level of theory is used for the remainder of the molecule. The ONIOM results compare favorably with those of conventional computational methods.
 

Poster Session
7:30 PM-10:00 PM, Wednesday, 13 September 2006 Moscone Center -- Hall D, Poster

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006