1. Condensed Matter and Radiation Sciences Division and Materials Science and Technology Division, Naval Research Laboratory, Washington, DC 20375-5000, USA.
2. Geophysical Laboratory and Center for High Pressure Research, Carnegie Institution of Washingto, Washington, DC 20015-1305, USA.
3. Chemistry Division, Research Department, Naval Air Warfare Center, Weapons Division, China Lake, CA 93555, USA.
4. Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, MD 20742, USA.