Beyond mean-field approximations for accurate and computationally efficient models of on-lattice chemical kinetics

Abstract

Assessment of mean-field microkinetic models for CO methanation on stepped metal surfaces using accelerated kinetic Monte Carlo The Journal of Chemical Physics 147, 152705 (2017) Modeling the kinetics of surface catalyzed reactions is essential for the design of reactors and chemical processes. The majority of microkinetic models employ mean-field approximations, which lead to an approximate description of catalytic kinetics by assuming spatially uncorrelated adsorbates. On the other hand, kinetic Monte Carlo (KMC) methods provide a discrete-space continuous-time stochastic formulation that enables an accurate treatment of spatial correlations in the adlayer, but at a significant computation cost. In this work, we use the so-called cluster mean-field approach to develop higher order approximations that systematically increase the accuracy of kinetic models by treating spatial correlations at a progressively higher level of detail. We further demonstrate our approach on a reduced model for NO oxidation incorporating first nearest-neighbor lateral interactions and construct a sequence of approximations of increasingly higher accuracy, which we compare with KMC and mean-field. The latter is found to perform rather poorly, overestimating the turnover frequency by several orders of magnitude for this system. On the other hand, our approximations, while more computationally intense than the traditional mean-field treatment, still achieve tremendous computational savings compared to KMC simulations, thereby opening the way for employing them in multiscale modeling frameworks.

Multiscale modelling of CO2 reduction to methanol over industrial Cu/ZnO/Al2O3 heterogeneous catalyst: Linking ab initio surface reaction kinetics with reactor fluid dynamics

“…Kinetic Monte Carlo (KMC) simulations were performed to study the evolution of a catalytic surface. We used the KMC software package Zacros 2.0 (Pineda and Stamatakis, 2017;Stamatakis and Vlachos, 2011a;Vignola et al, 2017), which uses a graph-theoretical implementation of KMC. We define a lattice structure, a reaction mechanism, an energetics model and reaction conditions.…”

Towardsoperandocomputational modeling in heterogeneous catalysis

“…The mean-field approximation implies that the adsorbates are not correlated spatially and therefore their mutual interactions are neglected. Although the development of more advanced kinetic modeling approaches accounting for such correlation effects is an active field of research, 288 – 290 the conceptual simplicity and ease of their practical implementation determine the success and widespread utilization of the mean-field phenomenological kinetic modeling approaches.…”

Micro-Kinetic Modelling of CO-TPD from Fe(100)—Incorporating Lateral Interactions

“…In this study, we used the Zacros, version 2.0, software package [38][39][40][41] which is based on the graph-theoretical kinetic Monte Carlo framework [39]. Detailed descriptions of this package and its implementation can be found elsewhere [40,41]. Briefly, the total lattice energy Hamiltonian, H(σ), is calculated using the cluster expansion approach [40]:…”