Title：New Findings in Materials in Extreme Environments

Speaker：Russell J. Hemley, Departments of Physics and Chemistry, University of Illinois at Chicago, Chicago IL 60607; Distinguished Chair in the Natural Sciences.

Time：April 10, 2019 (Wednesday) 14:30 PM

Venue：Central Campus, Tang Aoqing Building C Area 603 Lecture Hall

Abstract：

Extreme pressures and temperatures produce profound effects on structure, bonding and electronic character of atoms and molecules, molding matter to make new materials. A growing number of novel materials and phenomena are being documented over the broad range of conditions using both static and dynamic multimegabar (e.g., >300 GPa) pressures that can now be generated in the laboratory. The results are leading to altogether new structures, electronic phenomena and potentially useful materials, with implications beyond condensed matter physics to geophysics, planetary physics, astrophysics, and at more modest conditions even biophysics. Because of its quantum character and putatively simple electronic structure, the behavior of hydrogen has been of particular interest. Recent studies of hydrogen have uncovered new transformations to increasingly metallic states in both the solid and fluid using static and dynamic compression methods to multimegabar pressures. There have also been important recent findings in hydrogen-rich systems in a variety of chemical environments at these conditions. Most notable is our discovery of a new class of materials – superhydrides – and the observation of near room-temperature superconductivity in these systems, specifically lanthanum superhydrides with a Tc above 260 K near 200 GPa.