The water-dimer formation and its encapsulation into D2(22)-C84 and D2d(23)-C84 fullerenes is computed, following similar evaluations [1] with C60. The water-dimer equilibrium populations are calculated using the potential-energy change from the ab initio G3 theory and anharmonic partition functions from the MP2/AUG-cc-pVQZ approach. The encapsulation energetics is treated at the M06-2X/6-31++G** level and it is found that the water-dimer storage in C84 is attractive, yielding an energy gain of more than 10kcal/mol. This substantial encapsulation energy together with the computed temperature increase of the water-dimer population in the saturated steam suggest that the (H2O)2@C84 endohedrals could be produced in a high-temperature/high-pressure approach similarly to encapsulation of rare gases in fullerenes.

[1] F. Uhlik, Z. Slanina, S.-L. Lee, B.-C. Wang, L. Adamowicz, S. Nagase, J. Comput. Theor. Nanosci. 12, 959 (2015); 12, 2622 (2015).