Ab initio structure determination of low-molecular-weight compounds using synchrotron radiation Laue diffraction

The potential of using polychromatic synchrotron radiation for ab initio st ructure determination of low-molecular-weight compounds is investigated. Th ree different organic compounds were studied. For each of the structures th e cell volume was determined with the aid of a Zr attenuator that was place d in the direct beam to obtain a sharp lambda(min) edge. Space-group determ ination did not prove to be complicated; it was aided by deconvolution of t he multiple spots. Two low-temperature data sets were collected, and it app eared that spot streaking owing to the inherent increase of mosaicity due t o freezing was not too detrimental to the application of the Laue method. A lthough both the R-merge values (around 12%) and the final R-1 values (arou nd 10%) are higher than usually found in monochromatic experiments, all str uctures show reasonable geometry. Comparison of one of the structures with a reference structure obtained with monochromatic data shows an r.m.s. devi ation between the 21 non-H-atom positions of 0.019 Angstrom.