A general theory for the diffraction line profiles of h.c.p. and f.c.c. polycrystals containing stacking faults

A general theory is proposed for the diffraction line profiles of powders of close-packed crystals containing stacking faults. It covers two theories; one is the Gevers theory which combines the `growth fault' with s (Reichweite) = 2 and the `single deformation fault' in h.c.p., and the other the theory of the 'extended growth fault' with s = 2. The anomalies in the line profiles of nearly h.c.p. and nearly f.c.c. powders, i. e. peak displacement, broadening, and asymmetry, are expressed as functions of stacking fault probabilities. The conclusion is as follows. Although the Gevers-Warren theory, which is being widely used for interpreting experimental results, is useful from the practical point of view, the fault probabilities obtained by use of this theory should only be taken as very rough estimates.