Abstract
The magnitude of intramolecular basis set superposition error (BSSE) is revealed via computing systematic trends in molecular properties. This type of error is largely neglected in the study of the chemical properties of small molecules and it has historically been analyzed just in the study of large molecules and processes dominated by non-covalent interactions (typically dimerization or molecular complexation and recognition events). In this work we try to provide proof of the broader prevalence of this error, which permeates all types of electronic structure calculations, particularly when employing insufficiently large basis sets.
Highlights
Basis set superposition error (BSSE) is a fundamental issue in electronic structure calculations [1].Its academic definition is usually based on the monomer/dimer dichotomy: In an electronic structure calculation, the energy contribution of each monomer to the dimer is artificially shifted down with respect to that of the isolated monomer due to the stabilizing effect of overlapping basis belonging to the other monomer.This problem is indissoluble with the use of atom centered basis sets but it is worth noting that alternatives, such as the use of plane waves as basis sets, exist in which the basis set superposition error (BSSE) is avoided
That the average percentage errors are greater in the calculation of this second property. This is likely not assignable to the density functionals themselves, but to the approximations that are taken for the calculation of the thermal corrections to the electronic energy as mentioned in the methods section. These results have clearly revealed the existence of intramolecular BSSE in chemical reactivity, finding that its impact is not negligible when reaction enthalpies and free energies are computed with very popular basis sets (like 6-31G(d) and 6-31+G(d,p))
The goal of this work is to showcase the relevance of this error in chemical reactions and not to focus on how to solve this problem, a possible way to deal with this intramolecular BSSE could be based on dividing a single molecule into different fragments and calculating the energy as is done for the evaluation of the intermolecular BSSE using ghost functions in other parts of the molecule
Summary
Its academic definition is usually based on the monomer/dimer dichotomy: In an electronic structure calculation, the energy contribution of each monomer to the dimer is artificially shifted down with respect to that of the isolated monomer due to the stabilizing effect of overlapping basis belonging to the other monomer. This problem is indissoluble with the use of atom centered basis sets (which are usually Gaussian functions) but it is worth noting that alternatives, such as the use of plane waves as basis sets, exist in which the BSSE is avoided. In weak interactions, like those found in DNA base pairs and in host–guest complexes, both natural and artificial, this error cannot be ignored because it may account for a large fraction of the weak interaction being computed
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