On the use of the Boys-Bernardi function counterpoise procedure to correctbarrier heights for basis set superposition error

The application of Boys-Bernardi's function counterpoise procedure to corre ct for the basis set superposition error when computing barrier heights ass ociated with transition structures using well-balanced basis sets is analyz ed in detail. It is shown that Emsley et al.'s formulation of the counterpo ise method including the fragment relaxation terms may involve considerable errors when the relative orientation of the reference fragments is very di fferent in the two chemical species defining the energy barrier. (C) 2001 E lsevier Science B.V. All rights reserved.