Motion of guest molecules in clathrates

First the term clathrates is explained and illustrated more precisely on the three examples ice clathrate, urea clathrate, and quinol clathrate. Then a review of experimental results, which exist in the literature in the following domains, is given: Thermodynamic studies, dielectric relaxation, far infrared, infrared, and Raman spectroscopic studies, nuclear magnetic and nuclear quadrupole resonance, electron paramagnetic resonance, magnetic susceptibility, and neutron scattering. Emphasis is laid on the informations of the dynamical behaviour. The results given by several methods for the same inclusion and the results given by one method for different systems are compared. Finally a model is developed, which describes the movements of the guest molecules, assuming in a first step, that there is no interaction between molecules of the neighbouring cages. After this the forces between molecules in neighbouring cages are taken into account. (orig.)