Structure and stability of the sH binary hydrate cavity and host-guest versus guest-guest interactions therein: A DFT approach

The intrinsic ability of clathrate hydrates to encage gaseous molecules is explored. Encapsulation ability depends on the cavity size and the type of guest gaseous species in addition to the physical parameters, temperature and pressure. Here we have reported the structure, stability and nature of interaction in dissimilar guest occupied sH hydrate cavity. Diatomic gas molecules and small polyatomic hydrocarbons are considered as guests. The irregular icosahedron (5(12)6(8)) cavity of sH hydrate is the host. Different thermodynamic parameters for the guest molecules encapsulation were calculated using three different hybrid DFT functionals, B3LYP, M05-2X, M06, and moreover using dispersion correction (PBE0-D3). With the consideration of large H-bonded systems the 6-31G* and cc-pVTZ basis sets were used for two set of computations. To disclose the nature of interaction between the host-guest systems as well as the interaction between the guest molecules inside the host the non-covalent interaction (NCI) indices and energy decomposition analysis (EDA) were done. Impact of host-guest and guest-guest interactions are discussed.

Automated summary

This study explores the ability of clathrate hydrates to encapsulate gaseous molecules. The encapsulation ability depends on factors such as cavity size, guest gaseous species, temperature, and pressure. The structure, stability, and interaction nature of dissimilar guest occupied sH hydrate cavity are investigated, considering diatomic gas molecules and small polyatomic hydrocarbons as guests. Different hybrid DFT functionals (B3LYP, M05-2X, M06) and dispersion correction (PBE0-D3) are used to calculate the thermodynamic parameters for guest molecules encapsulation. The non-covalent interaction (NCI) indices and energy decomposition analysis (EDA) are employed to understand the nature of interaction between host-guest and guest-guest systems.