Diffraction by face-centered cubic crystals containing extrinsic stacking faults

Abstract

The diffraction pattern of a face-centered cubic crystal containing an arbitrary density of extrinsic faults is derived. The derivation is subject to the restriction that the crystal be infinite with infinitely extended faults distributed at random on one set of parallel close-packed planes. Although both extrinsic and intrinsic stacking faults shift and broaden the same Bragg reflections, there are marked differences in behavior which make them readily distinguishable. The peak shift produced by a low density of extrinsic faults is in a direction opposite to the shift produced by intrinsic faulting. At higher extrinsic fault densities the shifted reflections show two peaks: a new peak arises near the hexagonal position, moving to the twin position as the density of faulting approaches unity. The broadening is asymmetric at all fault densities.