Even so, the FBH approach strikes us as the more reasonable one, especially where anions are involved, because Becke's approach depends only on the positions of the atoms (along with the empirical atomic radii), whereas the weight function defined in Eq. ( ) respects the diffuseness of the isolated anions's wave function. In the present context, this almost inevitably means that the extent of anion → water CT is smaller when the FBH approach is used, because the tails of the X -wave function cause a larger region of space to contribute to that fragment's integrated electron number, N X . As an example, Fig. presents E CT computed using both methods, for each snapshot of I -(aq) in bulk water. The results are considerably different depending on which method is used to count electrons, with the FBH approach compressing the CT energy into the interval 0 > E CT > -2 kcal/mol whereas the Becke procedure affords values of |E CT | as large as 20 kcal/mol. The latter value is comparable to the the average magnitude of the total SAPT0 induction energy, which is E ind = -22.3 kcal/mol for I -(aq) in bulk water. (Note that energy components corresponding to attractive interactions are negative.)