Development of New Diamond Cell Technology for Ultrahigh-Pressure Single-Crystal Structure Analysis Using X-ray Diffraction

Carnegie Institution Of Washington, Washington DC

Investigators

Abstract

0217389 Mao, Dera, Prewitt In recent years, increasing interest in ultrahigh-pressure research results primarily from the unique possibility to simulate in the laboratory the conditions that are characteristic of deep geological environments. The primary tool for achieving static pressures above about 25 GPa is the diamond anvil cell (DAC). Apart from isothermal compression studies, the DAC can also be used for in-situ experiments from room pressure to several megabars at temperatures from close to 0 K to several thousands of degrees. Most structure analysis at pressures above about 10 GPa has been limited to polycrystalline samples because the technology for single-crystal diffraction studies at higher pressures is not well-developed. This project will extend the pressure capability of single-crystal structure analysis from 10 to 120 GPa and even higher pressures. This pressure region is extraordinarily rich in phenomena that dramatically change electronic, magnetic, thermal, elastic, and bonding properties of materials. Precise determination of atomic positions and electron distributions accompanying these changes is the key for understanding the processes. The experimental and computational techniques we are planning to develop will make possible ultrahigh-pressure crystal-structure studies with both laboratory-based and synchrotron x-ray sources. With new developments in sample gaskets, pressure media, diamond anvils, backing plates, and diamond cell design, we will be able to bring a >(10 ?m)3 sample of an unstrained single crystal to the pressures stated above. Experiments based on these developments will provide definitive long-sought answers to important scientific questions in Earth, planetary, and materials sciences, including the fundamental changes of silicates, oxides, ices, and condensed gases that are the main components of deep planetary interiors.