Establishing the LaMnO3 Surface Phase Diagram in an Oxygen Environment: An ab Initio Kinetic Monte Carlo Simulation Study

We employ first principles methods to simulate the steady-state catalytic interaction of oxygen with the LaMnO3(001) surface under varying levels of oxidative environment. First, density-functional theory together with transition-state theory is used to obtain the energetics and activation barriers of the relevant elementary surface chemical processes. The results were subsequently fed into a kinetic Monte Carlo (kMC) simulation scheme to explicitly account for the correlations, fluctuations, and spatial distributions of the oxygen adatoms and ad-molecules at the surface of the catalyst under steady-state conditions. Adsorbate-adsorbate lateral interactions and influence of the local environment on the reaction kinetics were adequately taken into account to compute (p, T) surface phase diagrams under equilibrium and metastable situations. The kMC-based approach allows us to describe the kinetics-related effects such as the influence of the thermochemical history of the sample on the metastable regions of the (p, T) surface phase diagram. Features of the computed metastable phase diagrams are in excellent correspondence with available temperature-programmed desorption and catalysis experiments.