X-ray diffraction studies of RbBr-RbI mixed crystals

Mixed crystals of RbBr and RbI have been prepared from melt. Using an X-ray diffractometer powder patterns have been recorded. The lattice constants show slightly positive deviations from Vegard’s law. From the integrated intensities, the mean Debye-Waller factor has been determined. The Debye-Waller factor shows a highly non-linear composition dependence with positive deviations from linearity, the values for intermediate compositions exceeding those for the end members. The Debye temperatures calculated from the Debye-Waller factors show a non-linear composition dependence with negative deviations from linearity.