Scattering patterns with a PSD
The 2-dimensional Position Sensitive Detector on D19 has served on several occasions in the discovery and detailed analysis of non-Bragg scattering. One example is the study of an Al-Li-Cu based structure Al6(Cu,Zn)Li3, which is tetragonal with a=14Å and c=82Å. In the first instance D19 permitted the collection of a large number of reflections, and as the long c-axis was mounted along the long axis of the detector, which is ±32° in the vertical direction, several reflections could be recorded simultaneously. During these measurements additional large intensities were observed between some Bragg reflections. An example is shown in the figure below (Fig.1), where a scan through the 641 is depicted. Additional scattering is detected between 641 and 640.
Employing the complete information the Bragg intensity could be separated from the additional scattering. In the present case this scattering is probably not due to any characterisable disorder in the crystal, and the structure analysis is now under way on the Bragg intensities.
click on figure for more details (Fig.1)
Recording on the D19 PSD of the scattering near 641. The crystal is rotated around a vertical axis, omega, and the µ-axis is the vertical direction of the detector. In all there are 25 stills at intervals of 0.1°. The large peak to the left is non-Bragg scattering, while the two small peaks are 640 and 641.
Last updated by Andrew Crowe on 14/02/1996
click on figure for more details (Fig.1)