Alternate Complexes and Geometries

Substitution of the hydrogen atoms by alkyl groups appears to exert a minimal impact on the angular aspects of the calculated geometries. As an example, Amos et al. optimized 

The basis set superposition errors of the H2Y-HX complexes are comparable to those observed for HjZ-HX, listed earlier in Table 2.3 for a variety of basis sets. One interesting difference is that whereas the MP2 contribution to the binding energy of H3N--HF is attractive, albeit by less than 1 kcal, the correlation contribution in H20--HF is close to zero, with some basis sets yielding a small repulsive contribution after primary BSSE is accounted for. 

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