1. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
2. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
3. Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China
4. HPSynC, Geophysical Laboratory, Carnegie Institution of Washington, Argonne, Illinois 60439, United States
5. Department of Materials Science, Northwestern University, Evanston, Illinois 60208, United States