HIGH PRESSURE STRUCTURES OF GROUP V ELEMENTS AND GROUP IV-VI COMPOUNDS. J. Maclean¹, P. D. Hatton², J. Crain^l, K. D. M. Harris³, B. M. Kariuki³, F. Wu⁴, R. J. Cernik^{5, 1}Department of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, UK, ²Department of Physics, University of Durham, Durham, DH1 3LE, UK, ³School of Chemistry, Birmingham University, Birmingham, UK, ⁴Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 1000 80, P.R.China, ⁵CLRC, Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK

Using two-dimensional data collection techniques combined with synchrotron x-ray powder diffraction, similar high-pressure phases have been observed to exist in the group V elements Sb and Bi, and the group IV-VI compounds PbS, PbSe, and PbTe.

Our high-resolution angle-dispersive data, collected using image plates from samples within diamond anvil high-pressure cells, has shown that one high-pressure structure type is common to all five materials we have studied. The structures offer a transition route to a body-centered cubic phase in Sb and Bi, and to a CsCl-type structure in the Pb-chalcogenides.

The final structure solutions were aided by a new technique involving a Monte-Carlo algorithm. This method, originally used in studies of molecular crystals, was modified to allow us to locate atomic positions accurately enough to be used in conventional Rietveld refinements.