we need the enthalpy corrections between elements in their reference state (ES) and isolated atoms (A), i.e., ∆H f (A := C, 0 K) = H f (C, isolated atom, 0 K) -H f (C, graphite, 0 K). These corrections are usually obtained from experiments and very accurate QM calculations, and their values are well-tabulated with high accuracy. In addition, we need to add the AEC that relates the single point energy of isolated atoms to the QM zero of energy for a chosen level of theory, where AEC is applied to each atom in a molecule. Although we take H f (C, graphite, 0 K) as an example, the calculation of H f (H 2 , 0 K) follows the same logic.