Orientational disorder in plastic molecular crystals II. - Neutron scattering and orientational dynamics

2014 In this paper, it is shown how the formalism of the canonical symmetry adapted functions can be used to analyse neutron scattering data related to orientationally disordered molecular crystals when the rotational dynamics of the molecule is assumed to be independent of the lattice dynamics. In this approximation, the rotational contribution to the intermediate scattering function is expanded in terms of correlations between the symmetry adapted functions of the molecular orientations. The site and molecular symmetry are taken into account to derive the complete set of independent correlation functions and to find which of them can be measured through neutron coherent and incoherent scattering experiments performed on single crystals or powder sample. Besides, it is shown that the orientational probability density function can be fully determined from the elastic part of incoherent neutron scattering. J. Physique 41 (1980) 1053-1065 SEPTEMBRE 1980, p Classification Physics Abstracts 02.20 63.50 78.30