The superposition error problem: The (HF) 2 and (H 2O) 2 complexes at the SCF and MP2 levels

Abstract

The title calculations were performed with the aim of providing data for the critical examination of the utility of the basis set superposition error (BSSE) correction. The main results obtained are as follows. The SCF interaction energies corrected for the BSSE and evaluated with the basis sets of split-valence and DZ origin are similar. With the stabilization energy, both the basis set superposition error and the intersystem correlation energy are important. MP2 stabilization energies are only slightly dependent on basis set for basis sets of DZ + P or better quality. The basis set superposition error at both the SCF and MP2 levels remains almost unchanged when passing from the 6–31G* to the 6–311G(2 d, 2 p) basis set. At the SCF level sufficiently accurate geometries were obtained with the standard 6–31G* basis set. Optimization at the MP2 level with this and larger basis sets brings about only small changes with respect to optimum SCF geometries.