1. The
Cherry L. Emerson Center for Scientific Computation, Emory University, 1515
Dickey Drive, Atlanta, Georgia 30322, United States
2. Department
of Chemistry, University of Wisconsin—Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
3. Department
of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
4. Department
of Chemistry, Stanford University, Stanford, California 94305, United States