on
large numbers of processors.

<H2>Acknowledgments</H2>

 <P>This work was performed under the auspices of the High Performance
Computing and Communications Program of the Office of Scientific
Computing, U.S.  Department of Energy under contract DE-AC6-76RLO 1830
with Battelle Memorial Institute which operates the Pacific Northwest
National Laboratory, a multiprogram national laboratory.  This work
has made extensive use of software developed by the Molecular Science
Software Group of the Environmental Mo