1. Department
of Applied Physics and Materials Science, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
2. Thermal
Energy Conversion Technologies Group, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, California 91109, United States
3. Max Planck Institute
for Chemical Physics of Solids, Nöthnitzer
Strasse 40, Dresden 01187, Germany