Application of CCSD(T)/(ECP+GCM) for studying gas-phase electron and proton affinities

The aim of this work is to analyze high level [CCSD(T)/ECP + GCM] calculations employed to determine the electron and proton affinities (EA and PA) of a set of molecules. The basis sets were developed for pseudopotential using the GCM procedure. This technique is potentially useful for large molecules containing heavy atoms. It can be classified as a quantum chemistry composite method, and achieves similar performance to the Gaussian theory (G2, G3, and G4) and CBS methods at a lower computational cost. The root mean square deviations (delta(rmsd)) of EA and PA, in comparison to the experimental results, obtained were 0.15 eV and 4.14 kJ mol (1), respectively. (C) 2008 Wiley Periodicals, Inc.