Results for E a (Fig. ) and for ∆ rxn E (Fig. ) demonstrate that n-body results with either vacuum (ε = 1) or PCM (ε = 4) boundary conditions converge similarly, although the PCM-based error is smaller at the n = 2 level. Unlike the charge-coordinated results for COMT, where the fragments are large and thus many-body effects are small, here the n = 1 results are unacceptable but twobody results with low-dielectric boundary conditions are rather good.