QZVP stands for a quadruple-zeta valence basis set with polarization functions, and the prefix aug- denotes additional diffuse functions on nonhydrogen atoms, which were taken from Dunning s aug-cc-pVQZ basis set. For C and H, this corresponds to and , respectively, where the numbers in brackets denote shells of contracted Gaussian-type orbitals , as usual. We will take the aug-QZVP results as a reference to assess the effect of smaller basis sets.