I.K. Bdikin, N.N. Kolesnikov, and V.Sh. Shekhtman
X-ray Diffraction Effects in Defect ZnS Single Crystals.

Abstract:
X-ray techniques have been used to investigate single ZnS crystals grown according to Bridgman by vertical oriented crystallization under an argon pressure of 5-6 MPa. These crystals consist of microtwins misoriented to each other by 60^o about the axis {111}. Some reflections show multiple diffraction. This is manifested in extra narrow lines on the topographs and additional reflections on the diffraction patterns.
The model of the multiple diffraction, based on the assumption that the effect increases when the phase invariant is equal to zero, has been considered. This model describes the experiment satisfactorily.