H$_2$, HD and D$_2$ in the small cage of structure II clathrate hydrate: Vibrational frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates

David Lauvergnat (1) , Peter Felker (2) , Yohann Scribano (3) , David Benoit (4) , Zlatko Bačić (5)

1 LCPO - Laboratoire de Chimie Physique D'Orsay
2 UCLA-CS - Computer Science Department [UCLA]
3 LUPM - Laboratoire Univers et Particules de Montpellier
4 University of Hull [United Kingdom]
5 NYU - New York University [New York]

We report the first fully coupled quantum 6D bound-state calculations of the vibration-translation-rotation (VTR) eigenstates of a fexible H$_2$, HD, and D$_2$molecule confined in the small cage of the sII clathrate hydrate embedded in larger hydrate domains, treated as rigid. These calculations extend to the first excited (v = 1) vibrational state of H$_2$ and the two isotopologues, and allow direct computationof its vibrational frequency shift. For the caged H$_2$, the fundamental translational excitations, the rotational $j = 0 \rightarrow 1$ transitions, and the frequency shifts of the stretch fundamental from these quantum 6D calculations are in excellent agreement with the corresponding results of the recent quantum 5D (rigid H$_2$) treatment [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)].

Domaines: Physique Quantique [quant-ph]; Agrégats Moléculaires et Atomiques [physics.atm-clus]; Chimie-Physique [physics.chem-ph]; Physique Numérique [physics.comp-ph]

David Lauvergnat, Peter Felker, Yohann Scribano, David Benoit, Zlatko Bačić. H$_2$, HD and D$_2$ in the small cage of structure II clathrate hydrate: Vibrational frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates. Journal of Chemical Physics, 2019, 150, pp.154303. ⟨10.1063/1.5090573⟩. ⟨hal-01962172⟩