Dislocation multiribbons and stacking faults in chromium Chloride and chromium bromide

The structure of dislocation multiribbons in chromium chloride and chromium bromide is analysed in detail. The ribbons consist either of four or six partials separated by regions of stacking faults. The relative magnitude of the stacking fault energies as deduced from the spacings of the partials, can be correlated with the arrangements of layers in the different faults. In particular the geomerty of triply charged chromium ions seems to be of importance in determining the magnitude of the stacking fault energy. If the chromium ions in successive layers come vertically above one another a high energy fault results. The phenomenon of "partial intersection" of ribbons gives rise to tenfold ribbons. The networks resulting from intersecting families of ribbons are analysed in detail.