Accurate reaction barrier heights of pericyclic reactions: Surprisingly large deviations for the CBS-QB3 composite method and their consequences in DFT benchmark studies

Abstract

© 2015 Wiley Periodicals, Inc.Accurate barrier heights are obtained for the 26 pericyclic reactions in the BHPERI dataset by means of the high-level Wn-F12 thermochemical protocols. Very often, the complete basis set (CBS)-type composite methods are used in similar situations, but herein it is shown that they in fact result in surprisingly large errors with root mean square deviations (RMSDs) of about 2.5 kcal mol-1. In comparison, other composite methods, particularly G4-type and estimated coupled cluster with singles, doubles, and quasiperturbative triple excitations [CCSD(T)/CBS] approaches, show deviations well below the chemical-accuracy threshold of 1 kcal mol-1. With the exception of ..