1. a Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering , Massachusetts Institute of Technology , 77 Massachusetts Avenue, Room 1–235A and B, Cambridge, Massachusetts, 02139, USA
2. b Center for Materials Science and Engineering , Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts, 02139, USA
3. c Center for Computational Engineering , Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts, 02139, USA E-mail: