QUANTUM TRANSLATION-ROTATION DYNAMICS OF HYDROGEN MOLECULES CONFINED IN THE CAGES OF CLATHRATE HYDRATES
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Date
2007
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Publisher
Ohio State University
Abstract
The coupled translation-rotation (T-R) eigenstates of a hydrogen molecule inside the small dodecahedral (H$_2$O)$_{20}$ cage of the structure II clathrate hydrate have been determined accurately by means of quantum 5D calculations, for {\it para}- and {\it ortho}-H$_2$} \underline{\textbf{110}}, 24806 (2006)}, as well as {\it ortho}- and {\it para}-D$_2$} \underline{\textbf{111}}, 2497 (2007)}. In addition, the ground-state properties of two and three {\it para}-H$_2$ and {\it ortho}-D$_2$ molecules confined in the small cage have been calculated rigorously using the diffusion Monte Carlo method$^b$. These calculations have provided a comprehensive picture of the quantum T-R dynamics of the encapsulated molecules. The translational modes exhibit negative anharmonicity; $j$ is a good rotational quantum number, with the threefold degeneracy of the $j=1$ level lifted completely. When two hydrogen molecules are confined, they are effectively excluded from the central region of the cage, and reside within a shell less than 2 bohrs wide. If time permits, the quantum dynamics results for multiple H$_2$/D$_2$ molecules inside the large (H$_2$O)$_{28}$ cage will be presented.
Description
Author Institution: Department of Chemistry, New York University, New York, NY 10003