Basis Set and Method Dependence in Quantum Theory of Atoms in Molecules Calculations for Covalent Bonds

The influence of various small- and medium-size basis sets used in Hartree - Fock (HF) and density functional theory (DFT)/B3LYP calculations on results of quantum theory of atoms in molecules based (QIAIM based) analysis of bond parameters is investigated for several single double and triple covalent bonds It is shown that in general HF, and DFT/B3LYP methods give very similar QTAIM results with respect to the basis set The smallest 6-31G basis set and DZ-quality basis sets of Dunning type lead to poor results in comparison to those obtained by the most reliable aug-cc-pVTZ On the contrary, 6-311++G(2df 2pd) and in a somewhat lesser extent 6-311++G(3df 3pd) basis sets give satisfactory values of QTAIM parameters is It is also demonstrated that QTAIM calculations may be sensitive for the method and basis set in the case of multiple and more polarized bonds