Structure factors from pseudo-Kossel line patterns

Abstract

Pseudo-Kossel lines are cones of Bragg reflections that contain information on the structure of single crystals. Nevertheless, they are not used in structure determination. The feasibility of obtaining a data set of structure factor amplitudes from a pseudo-Kossel line pattern measurement is presented in this paper. The experimental setup shown allows the detection of almost the complete cone pattern around the sample. The measurement process is significantly simpler than data collection with a conventional four-circle diffractometer. The extraction of structural information from the measured pattern completely separates from the data collection phase. The process consists of three main steps: determining the crystal lattice from the geometry of the cones, calculating the integrated intensities belonging to each reflection and finally solving/refining the structure in the usual manner. As an example, the pseudo-Kossel line pattern of a C60single crystal was recorded and analysed. The extracted single-crystal data set, fitted with the face-centred cubic structure of C60, yieldedR= 4.5% andRw= 7.7%. The advantages and drawbacks of this method compared with conventional single-crystal measurements are discussed. Two variants of the detection process in the method are also compared.