1. Materials Chemical and Computational Science Directorate, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
2. Department of Materials Science and Engineering, University of California Berkeley, Berkeley, California 94720, USA
3. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
4. Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
5. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
6. Kavli Energy Nanosciences Institute at Berkeley, Berkeley, California 94720, USA