Chapter 18 - High-pressure structure determination and refinement by X-ray diffraction

Abstract

The chapter reviews the methods required to obtain accurate structure refinements from high-pressure single-crystal X-ray diffraction measurements and examines the potential of new measurement methods with single crystals and synchrotron X-ray sources. High-pressure X-ray diffraction measurements have been traditionally made by single-crystal diffraction in the laboratory, using methods adopted from traditional crystallography. The measurements are made with radiation of a specific wavelength in an angle-dispersive mode. The diffracted beams from a powder specimen are much weaker than those from the same volume of a single crystal, and thus, synchrotrons are chosen as an X-ray source for high-pressure powder X-ray diffraction. The determination of the structure of a crystalline material at high pressures is dependent upon the accurate measurement of the intensities of X-ray or neutron beams diffracted by the sample, and the precise correction of the intensities for the various effects of the high-pressure device. In this context, the methods required to obtain accurate structure refinements from high-pressure single-crystal X-ray diffraction measurements are reviewed and the potential of new measurement methods with single crystals and synchrotron X-ray sources is assessed.