X-ray diffuse scattering from wurtzite-type compounds

The diffuse scattering of the wurtzite-type compounds β-AgI, CdS, CdSe, AlN, SiC, ZnO and ZnS has been investigated by X-ray diffraction using film methods, β-AgI, CdS and CdSe show strong non-radial diffuse streak patterns at room temperature, whereas the remaining compounds show only weak or no diffuse scattering. The pattern of the diffuse scattering consists of planes and rods running through the Bragg reflections of the reciprocal lattice of the wurtzite-type compounds. None of these planes and rods runs through the origin of the reciprocal lattice. Most of the diffuse intensity is concentrated in planes parallel to { 100 }* and in the rods parallel to a* and c* axes. High- and low-temperature experiments indicate a thermal origin of the diffuse scattering. The observed patterns can be explained by the uncorrelated thermal vibrations of structural units as chains and layers. The intensity shows a correlation to the ionicity and bond length of the investigated wurtzite-type compounds.