Ivan Michael Zeron, José Manuel Míguez, Bruno Mendiboure, Jesús Algaba, Felipe J. Blas J. Chem. Phys. 2022, https://doi.org/10.1063/5.0101746
Growth patterns and nucleation rate of carbon dioxide hydrates critically depends on the precise value of the hydrate – water interfacial free energy. There only exist in the literature two independent experimental measurements of this thermodynamic magnitude obtained by Uchida et al., 28(2)mJ/m2 , and by Anderson and workers, 30(3) mJ/m2. Recently, Algaba and collaborators have extended the Mold Integration method proposed by Espinosa and coworkers to deal with the CO2 hydrate-water interfacial free energy (Mold Integration – Host or MI-H). Computer simulations predict a value of 29(2)mJ/m2, in excellent agreement with experimental data. The method is based on the use a mold of attractive wells located at the crystallographic positions of the oxygen atoms of the water molecules in the equilibrium hydrate structure to induce the formation of a thin hydrate slab in the liquid phase at coexistence conditions. We propose here a new implementation of the Mold Integration technique using a mold of attractive wells located now at the crystallographic positions of the carbon atoms of the CO2 molecules in the equilibrium hydrate structure. We find that the new Mold Integration – Guest methodology, that does not introduce positional neither orientational information of the water molecules in the hydrate phase, is able to induce the formation of CO2 hydrates in an efficient way. More importantly, this new version of the method predicts a CO2 hydrate – water interfacial energy value of 30(2)mJ/m2, in excellent agreement with experimental data, which is also fully consistent with the results obtained using the previous methodology.