Basis set superposition error in atomic cluster calculations

In this work the basis set superposition error (BSSE) has been analyzed for the systems Cu-2, Cu-3, Cu-6 and Cu-13 as prototypes of metallic clusters. Various basis sets have been tested. In addition, pseudopotentials of 1- a nd 19-valence electrons have also been studied in relationship to the BSSE. The results are conclusive. At the present, it is almost impossible to do an all-electron calculation in transition-metal clusters without great erro r in basis set superposition, even for clusters of moderate size. The only solution seems to be using pseudopotentials with a carefully chosen basis s et. (C) 1999 Elsevier Science B.V. All rights reserved.