In previous work we have often used self-consistent charge embedding of the SCF monomer wave functions as a means to incorporate many-body polarization effects into a pairwise SAPT calculation, albeit implicitly . The present work does not make use of any charge embedding, however, and instead the X -(H 2 O) n system is treated as dimers, with (H 2 O) n as one monomer. In principle, charge embedding could be used to describe these clusters more efficiently as (n + 1)-body systems with monomers X - and H 2 O, but we have chosen not to do so here. The dimer approach makes the SAPT interaction energies more directly comparable to those obtained using the AMOEBA force field.