Host-guest and guest-guest interactions in noble gas hydrates

摘要

The encapsulation of noble gas atoms, helium, neon, argon and krypton in dodecahedral (DD) and its fused cages is studied using the dispersion corrected density functional theoretical method employing B97-D functional and cc-pVTZ basis set. The influence of an adjacent cage and the presence of a guest atom therein on the host-guest and the guest-guest interactions in noble gas hydrates are investigated. It is revealed that the host-guest interaction increases with an increase in the size of the encapsulated atom. The feasibility of encapsulation of guest species is analysed in terms of change in enthalpy (Delta H) and Gibbs free energy (Delta G). The results indicate that Kr@DD is stable at a relatively high temperature and lowpressure (260 K, 1 atm), whereas the encapsulation of Ne and Ar at the same temperature requires high pressure (similar to 100 atm). It is also found that the values of Delta H and Delta G for the encapsulation do not depend on the presence of an adjacent cage or the guest species trapped in the neighbouring cavity.