REINVESTIGATION OF γ-Na_2CO_3

摘要

r-Na2CO3 was the first incommensurate structure to be investigated with the superspace group approach. The refinement algorithms since then have matured. This structure was reinvestigated from new X-ray measurements and with a new version of MSR in order to obtain a satisfactory model for the high order satellites. The diffraction pattern features satellites up to fifth order using a conventional X-ray source. Anharmonic refinement results are presented including newly measured data with satellites up to fifth order. The results essentially agree with the predictions based on harmonic and the conventional superstructure models. The open problem of the lock-in transition at about 170K will be discussed.