Coincidence twist boundaries between crystals of MgO smoke

Twist boundaries have been observed on {001} surfaces between crystals of MgO smoke. Measurements of the angle of twist across 80 of these grain boundaries have revealed a preference for boundaries at 16.5±0.3°, 22.6±0.3°, and 36.6±0.3°. These angles agree with those predicted by the coincidence site model to within the accuracy of measurement. © 1970 The American Institute of Physics.