Correcting for basis set superposition error in aggregates containing more than two molecules: ambiguities in the calculation of the counterpoise correction

Abstract

The counterpoise correction (CP) for the basis set superposition error (BSSE) for multimolecular aggregates can (in principle) be calculated by several different procedures, which give significantly different results. Three of these procedures are discussed and illustrated with the HF---(HF) n ---HF H-bonding aggregate. The three methods are (a) proceeding as if a dimer were formed between a unit of HF added to the H end of the growing aggregate, (b) as above, but with the HF being added to the F end, and (c) using the difference between the calculated CPs for the two aggregates before and after addition of the last HF, where the CPs for each aggregate are calculated using each monomeric unit in each aggregate with the ghost orbitals of all the other monomers