From owner-chemistry _-at-_)ccl.net Mon Jul  1 07:10:01 2019
From: "John Simmie john.simmie..nuigalway.ie" <owner-chemistry a server.ccl.net>
To: CCL
Subject: CCL: BSSE correction for transition states
Message-Id: <-53777-190701024234-609-SYDJ03d/5BHVm8EDcoDvKA a server.ccl.net>
X-Original-From: "John  Simmie" <john.simmie,,nuigalway.ie>
Date: Mon, 1 Jul 2019 02:42:32 -0400


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