Probing intermolecular potential of hydrogen clathrates from high dimensional quantum simulations Author(s): Scribano Y., Lauvergnat David Invited Conference: Journées Hydrates 2022 (Rueil-Malmaison, FR, 2022-11-29) Abstract: Gas hydrates are nanoporous crystalline solids composed of hydrogen-bonded water molecules forming cages within which gaseous molecules are encapsulated. Since their initial discovery, interest in gas hydrates has grown exponentially from being of mere scientific curiosity to offering a potential new energy solution to the imminent energy crisis [1]. Gas hydrates are considered to be pivotal terrestrial and extraterrestrial ingredients, as they make up a great part of the Earth's seafloor sediments and play a role in extraterrestrial planetary formation scenari [2]. For example, clathrate hydrates of methane are extensively studied in astrophysics because they are suspected to be present on several planets, satellites and comets of the Solar System [3]. However, the description of such encapsulated molecular systems is often far from complete. Indeed, in such nanoscale confinement, the translational center-of-mass motions of the caged molecules are quantized and strongly coupled to the molecular rotations, which are quantized too. To interpret experimental data (like inelastic neutron scattering), theoretical tools are useful but we need to go beyond the simple harmonic approximation as the guest molecule presents very large amplitude motions (translation and rotation) and its interaction with the nanoscale cavity can be far from harmonic. A rigorous quantum treatment of the intricate coupled translation-rotation and/or vibration-translation-rotation (considering the molecular hydrogen stretching mode) dynamics of the caged diatomic molecules is far from a routine task. In this contribution, I will present a review on our recent progress in the development of efficient/accurate computational methods for the rigorous quantum treatment of the intricate coupled translation-rotation dynamics of the molecular hydrogen in water clathrates [4-7]. In particular, the efficiency of the computational method will highlight the impact of the condensed-phase environment on the spectroscopy of the confined molecule. Moreover, the efficiency of our computational scheme allows us to directly probe the quality of the considered intermolecular potentials (ranging from semiempirical to the most sophisticated ab initio potentials). Bibliography: [1] C. I. Ratcliffe, Energy fuels, 36 (2022) [2] B.K. Chastain et al., Planetary and Space Science, 55 (2009) [3] O. Mousis et al., Astrobiology, 15, 4 (2015) [4] A. Chen et al., J. Chem. Theory Comput., 18, 7 (2022) [5] D. Lauvergnat et al., J. Chem. Phys., 150 (2019) [6] D. Benoit et al., Faraday Discuss., 212, 533 (2018) [7] A. Powers et al., J. Chem. Phys., 148 (2018)