Fig. 1: Schematic representation of the effect of crystal mosaicity on diffraction.

a A perfect crystal with no mosaicity would yield high-quality diffraction data (below). Here the hypothetical mosaic blocks are perfectly aligned (green, blue, and red) and diffract together to form a sharp diffraction reflection with a high signal-to-noise ratio. b A crystal with defects would have high mosaicity that would yield data of lesser quality. Here, the hypothetical three mosaic blocks diffract at different angles and, when combined, result in a broadened diffraction reflection with a lower signal-to-noise ratio. Please note that the mosaic domains are not necessarily uniform or cuboid.