CCL: BSSE correction for transition states



 Sent to CCL by: "John  Simmie" [john.simmie++nuigalway.ie]
 The original post was concerned with bimolecular reactants & transition
 states and whether corrections are required. AFAIK the conclusion reached by
 Lendvay and Mayer [https://doi.org/10.1016/S0009-2614(98)01191-9]:
 "We performed a theoretical and numerical analysis of the different
 `counterpoise correction' (CP) schemes potentially applicable to correct for the
 basis set superposition error (BSSE) in the neighborhood of transition
 structures of chemical reactions. The analysis proved that neither of them is
 satisfactory: all CP versions result in either discontinuous potential surfaces
 or yield different energies for the same species in different reactions.
 Standard CP correction is unavoidable and satisfactory when loosely bound pre-
 or post-reaction complexes are studied. For transition structures, however,
 doing no correction is better than any available CP method."
 Has never been countermanded and most if not all practicing kineticists would
 apply a counterpoise correction to pre-reaction and post-reaction complexes if
 necessary but that's all.  Of course swamping with basis functions is also a
 good idea if that is feasible for the particular system being studied.
 John M. Simmie//School of Chemistry//National Univ. of Ireland, Galway