Intensity analysis for high-pressure powder diffraction using diamond anvil cells

An angle dispersive powder x-ray diffraction expeliment with an image plate (IP) and a diamond anvil cell has greatly improved data quality 1, which allows us to get an accurate structure including atomic parameters under pressure.The use of the synchrotron beam is recommended to get high angular resolution and sufficient intensity in powder pattems.The IP makes it possible to remove geometrical e!Tor easily on computer and to generate a 2theta versus intensity pattem.Then we can determine atomic parameters by the Rietveld or the least-square methods.A powder pattem of which structure is fully known also gives electron density dist1ibution map.The limiting number of the observed peaks causes tem1ination en•ors in both maps of the traditional Fourier synthesis and the previous maximum entropy method (MEM)2.To overcome this problem, we have developed a new MEM for high pressure experiments3 which can reduce the termination e!Tors by the same theory as the difference synthesis.