Résumé
The study of small/medium size molecules inside nanoscale cavities of diverse host material, e.g.,clathrates hydrates, cryogenic fluids (or superfluids), fullerenes, carbon nanotubes and zeolites, has receiveda great deal of attention over the past years due to their broad application domain (condensed matter physics,nanomaterial sciences, geoscience, quantum chemistry, astrophysical and planetary sciences, biophysics, ...).However the description of such systems is often far from complete. Indeed,in such nanoscale confinement, the motion of the encapsulated molecule is far from harmonic and is characterised by large amplitude motions. The translational center-of-mass motionsof the caged molecules are quantized and strongly coupled to themolecular rotations, which are quantized too.In this talk, I will present our recent progress in the Translation-Rotation (TR) and Vibration-Translation-Rotation (VRT) bound states calculation of guest molecules such as molecular hydrogen in a clathrate hydrate. Within this study, we have investigated the effect of a non-rigid description of a clathrate hydrate framework on the encapsulated molecular hydrogen eigenstates using an efficient sparse grid scheme which allow us to consider up to 65 degrees of freedom. Traditionally, the water cage structure is assumed to be rigid, thus ignoring the quantum nature of hydrogen nuclei in the water framework.