1. Department of Applied Physics, Stanford University, Stanford, California 94305, United States
2. Computational Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
3. Department of Chemistry, Stanford University, Stanford, California 94305, United States
4. Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
5. Computational Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
6. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States