Mind the basis set superposition error

In an ab initio calculation, when the inclusion of core electron correlation is required, the best approach is to use a basis set developed for the electrons that are correlated. However, when a basis set is used that has not been developed for the number of the electrons which are correlated in a calculation, the quantities calculated (geometry, binding energies, frequencies, etc.) need to be corrected for the basis set superposition error. Several cases are discussed and the proper line of action is emphasized. (C) 2010 Elsevier B.V. All rights reserved.