Adsorbate lateral interactions have recently attracted significant focus in the computational catalysis field, as they are responsible for ordering in the adsorbate overlayer, but also influence the activation energies of elementary events. Zacros treats such interactions within the general framework of cluster expansion Hamiltonians. This enables us to include long-range and many-body contributions in a simulation. Brønsted-Evans-Polanyi relations are used to correlate the activation energy of an elementary event with its reaction energy, thereby capturing the influence of neighbouring spectator adsorbates on barriers. This tutorial deals with setting up the Zacros input for a detailed cluster expansion Hamiltonian for O on Pt developed by Schneider and co-workers [J. Catal. (2012) 286: 88-94].
Adsorbate lateral interactions affect both the structure of the overlayer and the energetics of elementary events. They are thus responsible for spatial correlations and adsorbate ordering, and also result in spectator species influencing the stability of initial, transition or final states of elementary events, thereby affecting the activation energies thereof.1 A recent study by Schneider and co-workers2 demonstrated how such effects can be simulated using cluster expansions in Monte Carlo simulation combined with kinetic modelling. Such a cluster expansion Hamiltonian can be set up in Zacros file energetics_input.dat as shown in this tutorial.