Prediction of a new class of group 14 inclusion compounds encapsulating noble gases*

Group 14 elements (Si, Ge, Sn) exhibit a complex potential energy landscape and thus a vast array of allotropes emerge under extreme conditions. Employing density functional theory and molecular dynamics (MD) simulations, we predicted a new class of inclusion-type compounds of group 14 elements as host and noble gases (NG) as guest. The new compounds are structural analogs to the high-pressure phases of methane hydrate, a.k.a. “filled ices”. The stability of the compounds quickly increases with both the size of host and guest-host interaction. In particular, some Sn-NG systems are predicted to be thermodynamically stable. Our MD simulations show the crystallization of these compounds is kinetically favorable from the liquid of host in the presence of NG, as NG is found to induce a local ordering of liquid that structurally matches the compounds. To strengthen our conclusion, we have also employed high-level quantum chemistry calculations to examine the fundamental guest-host interaction, which allows further validating our predictions. Our study thus suggests a viable experimental route for synthesis under high pressure and high temperature. Experimental validation of our prediction is currently being carried out.