1. Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
2. Department of Civil and Environmental Engineering, Laboratory for Atomistic and Molecular Mechanics (LAMM), and Center for Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
3. Departments of Mechanical Engineering and Materials Science and Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.