The subscript A is the set of anchor species, in this case, A = [CH 4 , H 2 O, H 2 , Pt(111)]. ∆ A H of our chosen anchor species are 0 because it is a null reaction to form the anchor species from themselves. Eq. ( ) converts the zero-point corrected DFT energy of a single species into ∆ A H referenced to the set of anchor species, A. This problem can also be cast as a linear algebra problem for a set of species, typically the entire reaction mechanism. The linear algebra notation using the definitions in Table is as follows: