For simplicity, we integrated the entire slab directly into the elemental composition matrix, which is convenient when determining only ∆ A H of adsorbate and gas-phase species. It is possible to parameterize a microkinetic model with the derived ∆ A H from this method . However, the chemical potential of the slab can also be broken down into every atom, which is useful when investigating mixed transition metal, metal oxide, or metal carbide surfaces . Explicitly defining the chemical potentials of all atoms is often used to derive surface free energies γ .