Neutron scattering from orientationally disordered solids

In an orientationally disordered solid the equilibrium positions of the molecular centers of mass lie on an ordered three‐dimensional lattice, but the molecular orientations are disordered. The effects of this disorder can be observed in the scattered neutron distributions in several ways. The intensity of the Bragg reflections, particularly those with high Miller indices, is greatly reduced. Intense, diffuse scattering appears which may be distributed throughout reciprocal space. Well‐defined librational phonons are difficult to observe and the translational phonons are often very broad. A brief outline of the theory of neutron scattering from orientationally disordered solids is given and the information which may be derived from neutron scattering is discussed with reference to results on CBr₄, SF₆ and β‐N₂.