The accuracy of electronic structure calculations for gas/solid catalysis is typically limited to DFT because of the prohibitive computational cost of more advanced methods. Wellendorff et al. benchmarked predicted reaction energies for the adsorption of gas-phase molecules on transition metals with a range of different xc functionals with known experimental values and obtained the best results for the BEEF-vdW functional with uncertainties of ±30 kJ mol -1 (mean absolute error compared to the benchmark dataset) . Some studies employed higher levels of theory such as combinations of GGA and meta-GGA functionals , embedding techniques , random-phase approximation (RPA) , composite DFT/MP2/CCSD(T) methods 106-109 , CCSD(T) , and Quantum Monte Carlo to derive more accurate adsorption enthalpies. A review of beyond DFT methods is provided by Sauer 111 . However, even with highlevel methods, heterogeneous systems typically require pseudopotentials and other numerical approximations, leading to lower accuracy than what can be achieved for gas-phase systems. Another source of parametric uncertainty is the partition function used to compute the entropy and heat capacity, which are often approximated by assuming an ideal gas, harmonic oscillator, or hindered translator/rotor . The errors are typically smaller than errors in enthalpy but can still be substantial, as shown by more advanced techniques that account for anharmonicity .