Modeling the THF clathrate hydrate dynamics by combining molecular dynamics and quasi-elastic neutron scattering

The dynamics of the THF molecule encapsulated in the type II clathrate hydrate matches the MD-QENS observation time (typically 0.1-10 ps) between 100 K and 270 K. Spatial and time characteristics of the THF molecule's dynamics obtained by means of MD simulations are in agreement with those experimentally determined by means of quasielastic neutron scattering. A detailed model of the THF dynamics is then proposed through the calculations of MD-derived properties. Reorientational relaxation has been observed on a timescale of 0.7 +/- 0.1 ps at 270 K with activation energy of 3.0 +/- 0.3 kJ/mol in addition to a highly damped rotational excitation occurring in the plane of the THF molecule with a period of ca. 2 ps. Moreover, the anisotropic cage energy landscape of the THF clathrate hydrate is revealed through a comprehensive investigation of THF orientational distribution functions, revealing the occurrence of preferred orientation of the THF molecule within the cage. (C) 2017 Elsevier B.V. All rights reserved.