Research Interests

As a geophysicist, I have built a high-pressure research program at the Geophysical Laboratory, Carnegie Institution of Washington. My research includes pioneering and continuing work in the development of ultra-high-pressure technology and in the application of the technology to physics, chemistry, materials sciences, geophysics, geochemistry, and planetary sciences. Utilizing diamond anvil cell techniques, my colleagues and I have discovered numerous new physical and chemical phenomena at high pressures including pressure-induced amorphization and crystallization, change of chemical bonding (ionic, covalent, Van der Waals to metallic), and electronic and structural phase transitions. The behavior of hydrogen at ultrahigh pressure is a problem of fundamental interest. We have successfully compressed hydrogen and deuterium to pressures above 2.5 Mbar. We discovered and characterized several novel phase transitions including the molecular ordering and drastic change of oscillator strength. We also have conducted systematic studies of material properties at high pressures and temperatures. With these studies it becomes possible to construct geophysical and geochemical models of the Earth and planets based on direct experimental data.

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Section 15: Geology