where E X C denotes the correlation energy calculated with the def2-XZVP or (aug)-cc-pVXZ basis set. The extrapolated results are then labeled by def2-(T,Q)ZVP or (aug)-cc-pV(T,Q)Z, respectively. This two-point extrapolation formula was originally only applied to correlation-consistent basis sets. For computational efficiency, we employ the same extrapolation strategy also with the def2-(T,Q)ZVP basis sets in the following. Whether this is a robust way to systematically approach the basis set limit is not clear. But as will be shown below, these extrapolated results seem acceptable in comparison with the extrapolations based on Dunning's basis sets.