The method depends on the DFT energies of the reference species, in this case CH 4 , H 2 O, and H 2 . The approach is typi- cally used with this reference species set since it is equivalent to an isogyric reaction . However, other reference sets could be selected, in which case the final ∆ f H of the resulting reaction network and the resulting adsorption enthalpies will vary slightly depending on the selected reference species. For example, it is possible to use the least squares anchor set introduced in Section 4.2.3 to combine data from two thermochemical networks without explicitly selecting molecular references. In this case, all adsorption/desorption energies would be corrected by some amount, but on average, the squared difference between the DFTderived and ATcT enthalpies of formation would be minimized.