Examining the basis-set convergence of the F -(H 2 O) 6 energy components, we find that electrostatic energies (Fig. ) span a wide range but if the minimallyaugmented basis sets are excluded then all of the values of E elst lie between -175 and -172 kcal/mol. At the triple-ζ level it appears that diffuse functions can safely be deleted from the hydrogen atoms, as the def2-ha-TZVP and def2-TZVP values of E elst differ by only 0.2 kcal/mol. That said, the def2-TZVPD value (E elst = -174.4 kcal/mol) differs by 2 kcal/mol from the def2-QZVPD value (E elst = -172.2 kcal/mol), and in fact that def2-SVPD value is much closer: E elst = -174.6 kcal/mol. As we observed for S66, a double-ζ basis set with a full complement of diffuse functions can stand in for a triple-ζ basis set for electrostatics calculations.