The Influence of Twinning by Merohedry on Intensity Statistics

A simple test based on intensity statistics is presented for the detection of twinning by merohedry. Using relationships derived in the text, the twinning fraction of a crystal may be estimated from the intensity probability distribution. Unlike most methods for the detection of twinning, application of this test does not require knowledge of the twinning operation. Two possible mechanisms for increasing the apparent diffraction symmetry of a crystal, twinning by merohedry and crystal disorder, may be distinguished in certain cases by these procedures