X-ray diffraction from solids under nonhydrostatic compression - some recent studies

Diamond anvil cells have been extensively used to generate pressures up to a few hundred gigapascals. A fine X-ray beam from a synchrotron source permits recording of diffraction patterns from the pressurized samples. Such high pressures (stresses) however are not hydrostatic. Modeling of the stress state and resulting lattice strains in the sample give information on the compression behavior of solids. It is possible to derive the hydrostatic equation of state, shear strength and single-crystal elastic moduli by suitably interpreting the line shift data from powder diffraction patterns taken under nonhydrostatic compression. Nonhydrostatic compression leads to the broadening of diffraction lines. The analysis of temperature dependence of line-widths gives information on theology of solids. The developments in the field are reviewed. The origins of line-shift and line-width are discussed using a generalized approach. (C) 2004 Elsevier Ltd. All rights reserved.