Accurate ranking of CH4•(H2O)20 clusters with the density functional theory supplemental potential approach

By providing a customized empirical correction to density functional theory (DFT), the recently developed DFT-supplemental potential (SP) approach can provide a post-Hartree-Fock quality potential energy surface at the cost of DFT. The performance of DFT-SP is validated by calculating binding energies of small methane-water clusters. The method is used to rank several CH4 center dot(H2O)(20) minima previously identified by Hartke. The more accurate DFT-SP approach identifies methane on edge-sharing pentagonal prisms as the lowest energy configuration. The methane-centered-dodecahedron cage is less stable than the lowest minimum studied in this work by 6.2 kcal/mol.