| Résumé | The interactions between atoms, molecules, and ions ultimately determine the structural forms of solid materials, and in turn the crystal structure itself imposes potential fields around these components, which strongly influence their dynamic behavior in the solid. This article discusses the many ways in which solid-state NMR has been used to explore this intimate connection between crystal structure and dynamics, emphasizing how the interplay between crystal and molecular symmetry affects translational and rotational motions. Brief descriptions of theory are given and different aspects are highlighted with examples. NMR studies of dynamics can yield structural information which is complementary to diffraction data, such as internuclear distances, angles between rotational and crystal axes, and symmetry information. In a number of instances, such information has been used to improve or direct structural refinements, especially where there are problems of disorder. NMR gives aspects of local structure and is sensitive to dynamics on various timescales, in contrast with diffraction, which gives a long-range spatial average of electron density with little or no temporal information. NMR also provides a wealth of other information, including activation energies required to cross barriers, rotational rates or correlation times, and dynamic behavior around phase transitions. |
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