Moiré Pattern for a Crystal Containing a Stacking Fault

The author has previously given expressions for the amplitudes of waves transmitted and diffracted by a foil formed by the superposition of two perfect plate‐shaped parallel crystals. These are now generalised to the case in which one crystal contains a stacking fault parallel to the foil surface. The introduction of this stacking fault results in a displacement of the moiré interference pattern, its direction and spacing being, however, unaltered. Also the intensities of the bright and dark fringes, and the contrast between them, are found to vary spatially between the region of the fault and the regions of perfect crystal. The variation of these intensities as the fault moves away from the surface on which the wave is incident, towards the other surface, is discussed. Finally, if the stacking fault is not parallel to the surface it is found that the expressions derived for parallel stacking faults are valid to within the column approximation.