Experimental studies of simple molecular systems to pressures of 400 GPa (4 megabars) over a broad range of temperatures will be carried out in this project. The research takes advantage of numerous developments in diamond-anvil cell techniques, including advances in analytical methods that utilize synchrotron x-radiation, spallation neutron scattering, laser spectroscopies, and transport probes. Dense hydrogen and hydrogen-dominant simple molecular solids, alloys, and selected elements will be examined to search for theoretically predicted novel metallization and superconductivity. The crystal structures of newly discovered high-pressure phases, particularly archetypal elemental systems, will be determined using synchrotron x-ray and neutron diffraction techniques, and the electronic structures will be explored using new x-ray inelastic scattering methods. By improving our understanding of fundamental interactions in condensed matter, the project will impact areas such as nanoscience, planetary science, and energy. The project will advance technology necessary for studying matter under more extreme conditions. The research will seek to enhance capabilities major national facilities, and will train post-doctoral fellows as well as high school students, undergraduates, graduate students, and visiting investigators.

Nontechnical Abstract

This project will explore the nature of matter through experimental studies of simple molecular substances subjected to pressures reaching 4 megabars (4 million times atmospheric pressure) over a broad range of temperatures from near absolute zero to many thousands of degrees. The project takes advantage of numerous recent developments in the ability both to subject materials to these extreme conditions and to probe samples under those conditions with synchrotron x-ray, advanced neutron, laser, and magnetic and electrical methods. Hydrogen-rich molecules will be transformed into new kinds of metals and superconductors, and the nature of metallic hydrogen, a predicted entirely new state of matter, will be explored. The dramatic changes in crystal structure and chemical bonding expected for materials under extreme conditions will be determined using a variety of x-ray and neutron methods. The results impact materials science, nanoscience, planetary science, and astrophysics. The work will lead to development of new energetic materials, novel superconductors, gas storage materials, and superhard materials. The research will enhance capabilities at major national facilities, and will train high school students, undergraduates, graduate students, postdoctoral associates, and senior scientists. Impacts on both science and society broadly are therefore expected.

National Science Foundation (NSF)
Division of Materials Research (DMR)
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Guebre X. Tessema
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Carnegie Institution of Washington
United States
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