From Atomic Scale Ordering to Mesoscale Spatial Patterns in Surface Reactions: A Heterogeneous Coupled Lattice-Gas (HCLG) Simulation Approach

Jim Evans
Iowa State University

A challenge for the modeling of surface reaction-diffusion systems is to connect-the-length-scales from a realistic atomistic treatment of local ordering of reactants and reaction kinetics to an ''exact'' description of mesoscale spatial pattern formation. We describe a heterogeneous coupled lattice-gas (HCLG) approach. This multiscale modeling approach utilizes parallel kinetic Monte Carlo simulations of a lattice-gas (LG) reaction model to simultaneously and precisely determine both the local reaction kinetics as well as the non-trivial diffusive transport properties at various macroscopic "points'' distributed across the surface. These parallel simulations are appropriately coupled to reflect macroscopic mass transport across the surface via surface diffusion.

This HCLG method is demonstrated for bistable CO-oxidation reactions on surfaces. First, we discuss a simplified canonical LG model for CO-oxidation where surface transport of CO is reduced from a many-particle to a single-particle problem (although one with even more complexity than an "ant-in-the-labyrinth" type percolative diffusion problem). Second, we discuss development of a realistic treatment for CO-oxidation on Pd(100). This is a major challenge since ordering of adsorbed reactants, and thus the details of kinetics and transport, are determined by very weak adspecies
interactions for which DFT cannot yet provide reliable values.

Presentation (PowerPoint File)

Back to Workshop II: Multiscale Modeling in Condensed Matter and Materials Sciences, including Mini-Workshop: Time Acceleration Methods in Atomistic Simulations