For this reason, when comparing the DLPNO-CCSD(T)/CBS(normalPNO)//ωB97x-3c calculations to the NIST data, we aligned the values by adding a shift parameter to the NIST data that minimizes the RMSE of the values compared to the QM calculations. Prior to alignment, we observed a mean unsigned deviation of 1.2 kcal mol -1 between the QM values and the NIST data, indicative of systematic error. After alignment, we observed an RMSE value of 1.57 kcal mol -1 which we assign as the uncertainty of the gas-phase acidity QM calculations (see Figure ). For consistency, all ∆G o acid, gas (AH) data from NIST used in this work will be aligned to the QM data by shifting them by 1.2 kcal mol -1 .