ABSTRACT: A well-documented body of both experimental and theoretical studies seems to suggest systematic phase/chemical transformations of low Z molecular solids to covalent solids, ionic solids and, eventually, metallic solids under extreme conditions. Inspired by this emerging theme, we have performed an integrated research program of small-scale static and large-scale dynamic high pressure-temperature experiments using synchrotron X-rays, X-ray Free Electron Laser (XFEL) and the National Ignition Facility (NIF), to investigate the evolution of chemical bonding, crystal structure and properties of low Z solids under extreme conditions. In this talk, I will first briefly describe several fundamental principles governing the chemistry of low Z solids under extreme conditions and, then, present our recent results of (i) NIF-Discovery Science Campaign on ramp-compressed NaCl to 1TPa, (ii) MHz time-resolved X-ray diffraction (TR-XRD) at Eu-XFEL to probe the structure evolution of N₂ under rapid compression in dynamic-DAC, and (iii) KHz TR-XRD at APS to probe the formation of superionic ice phases under rapid heating in ramp laser-heated DAC.   

A short biography of Prof. Choong-Shik Yoo, WSU: Professor Yoo is Professor of Department of Chemistry and Institute for Shock Physics at Washington State University. Dr. Yoo’s research is focused on addressing fundamental materials problems under extreme pressure-temperature conditions of giant planetary interiors and their dynamic responses at an atomistic level. His research utilizes static and dynamic high-pressure capabilities coupled with the state-of-the-art laser spectroscopic methods and fast time-resolved x-ray diffraction and spectroscopy at the national and international synchrotron and XFEL facilities, as well as high-power lasers at the NIF at LLNL and EMC at LCLS. Prior to his arrival at WSU, he worked at the Lawrence Livermore National Laboratory where he developed and led a large multi-disciplinary research group in High Pressure Physics. Professor Yoo received his Ph.D. in Physical Chemistry in 1986 from UCLA and served as a vice President for the AIRAPT and co-chaired a APS-SCCM/AIRAPT joint conference in Seattle, 2013.