X-ray diffraction studies of highly-condensed matter

Powder diffraction studies at high pressure have long been hindered by the poor signal-to-noise that al ises as a result of the necessarily small sample. While white-beam energy-dispersive techniques have overcome the problem of poor signal, the unreliable intensities inherent to this technique have meant that no detailed crystallographic information has been obtainable. The field of high-pressure diffraction has recently been transformed, however, by the use of image-plate area detectors coupled with angle-dispersive techniques and monochromatic synchrotron radiation. Such techniques allow reliable atomic coordinates to be refined for the first time. in this paper a brief overview of image-plate techniques as implemented at SRS Daresbury is given, anti some of the difficulties encountered in high-pressure diffraction studies are described. Illustrations are given from recent structural studies of elements and binary semiconductors.