Accurate calculations of interaction energies of H-bonded clusters

COMP 209

Jun Cui, juc9@pitt.edu1, Valerie N. McCarthy, vam2@pitt.edu2, Richard A. Christie, richard@pro3.chem.pitt.edu1, and Kenneth D. Jordan, jordan@pitt.edu3. (1) Dept. of Chemistry and Center for Molecular and Materials Simulations, University of Pittsburgh, Pittsburgh, PA 15260, (2) Department of Chemistry, University of Pittsburgh, 219 Parkman Ave, Pittsburgh, PA 15260, (3) Department of Chemistry and Center for Molecular and Materials Simulations, University of Pittsburgh, Pittsburgh, PA 15260
The n-body decomposition procedure can serve as the basis of computationally efficient strategies for obtaining near CBS-limit MP2-level interaction energies of large H-bonded clusters. The key is the realization that the n ≥ 3 body interaction energies are relatively insensitive to the basis set, and that the major need for large basis sets is in describing the two-body interaction energies. In addition, most of the 3- and 4- body interaction terms are very small, and this has led us to develop a pre-screening algorithm to eliminate n ≥ 3 body contributions below a user-specified threshold. In my presentation, I describe this screening strategy and demonstrate its application to the (H2O)21 and (H2O)20CH4 clusters. With the use of screening, the computational effort to evaluate the net 3- and 4- body interaction energy is reduced by over an order of magnitude for the n=21 cluster.
 

Poster Session -- Sponsored by Novartis Institutes for BioMedical Research
6:00 PM-8:00 PM, Tuesday, 30 August 2005 Washington DC Convention Center -- Hall A, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, 29 August 2005 Washington DC Convention Center -- Hall A, Sci-Mix

Division of Computers in Chemistry

The 230th ACS National Meeting, in Washington, DC, Aug 28-Sept 1, 2005