1. Department of Applied Physics, Stanford University, Stanford, California 94305, United States
2. Google Brain, Mountain View, California 94043, United States
3. Department of Chemistry, Stanford University, Stanford, California 94305, United States
4. Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
5. Department of Materials Science and Engineering, Stanford University, Stanford, California 94304, United States