Probing structural chirality with high-energy synchrotron radiation

Abstract

The absolute structure has been determined for MnSi with data collected using synchrotron radiation withE= 78.3 keV (0.158 Å). At this energy, the resonant scattering contribution from MnSi is very small (f′Mn= −0.0397,f′′Mn= 0.0385,f′Si = −0.0197,f′′Si= 0.0027), but the large number of observed Bijvoet differences together with a wideQrange make absolute structure determination possible. A comparison with the data collected atE= 18 keV (0.68 Å) (f′Mn= 0.2858,f′′Mn= 0.6739,f′Si= 0.0653,f′′Si= 0.0646) for the same crystal shows the correctness of the absolute structure measured at the higher energy. A similar data collection has also been done atE= 65.3 keV (0.19 Å) for a single crystal of Fe0.7Co0.3Si with known absolute structure. In all cases, the absolute structure was correctly determined by analysing the statistical distribution of the chirality measure. Statistical descriptors of the refinements, the Flack parameter and the distribution of Parsons quotients are discussed for all presented experiments.