1. Laboratory for Atomistic and Molecular Mechanics (LAMM), Massachusetts Institute of Technology, 77 Massachusetts Ave. 1-165, Cambridge, Massachusetts 02139, USA
2. Institute of High Performance Computing, A*STAR, Singapore 138632, Singapore
3. Center for Computational Science and Engineering, Schwarzman College of Computing, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139, USA
4. Center for Materials Science and Engineering, 77 Massachusetts Ave, Cambridge, Massachusetts 02139, USA