1. Department of Mathematics, Penn State University, University Park, Pennsylvania 16802, United States
2. Kenneth S. Pitzer Theory Center and Department of Chemistry, University of California, Berkeley, California 94720, United States
3. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
4. Departments of Bioengineering and Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
5. Applied Mathematics and Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States