International Collaboration in Chemistry: First Principles Multi-Lattice Kinetic Monte Carlo Simulations of NOx Storage Reduction Catalysts
Final Report Abstract
Kinetic Monte Carlo (kMC) simulations have emerged as a key tool for microkinetic modeling in heterogeneous catalysis and other materials applications. Systems, where site-specificity of all elementary reactions allows a mapping onto a lattice of discrete active sites, can be addressed within the particularly efficient lattice kMC approach. At present, such efficiency is a prerequisite for quantitative so-called 1p-kMC simulations based on first-principles calculations. By construction, the conventional lattice kMC approach cannot directly be applied to (surface) morphological rearrangements, i.e. any type of phase transition that includes changes in the considered lattice site arrangement. As a first step to make such systems and phenomena accessible to 1p-kMC we developed a multi-lattice 1p-kMC approach, which is applicable to morphological transitions between commensurate crystalline lattices. As corresponding multi-lattice 1p-kMC models lead to a code complexity that exceeds the one conveniently handled with tailored code written from scratch, a central undertaking of the project was the development of a versatile and powerful software package, called kmos, which offers a most user-friendly implementation, execution, and evaluation of lattice kMC models of arbitrary complexity. Rather than providing a hard-coded scaffold that is generic enough to deal with any level of model and model complexity, the essential and completely novel idea of the kmos approach to kMC modeling is thereby to use a code generator to produce a tailored and thus highly efficient code from an abstract definition of a kMC model. The code is open source and within one year after its release already enjoys a rapidly growing user community of more than 30 groups worldwide. Showcase applications highlighting the capabilities of the code infrastructure address the surface reaction chemistry of exhaust catalysts operating at ambient and in particular time-varying conditions. This involves in particular a potential appearance and destruction of surface oxide phases on metal catalysts as the reactor conditions e.g. cycle from oxidative to reductive conditions in the operation of a NOx Storage Reduction (NSR) catalyst system.
Publications
- Role of Surface Oxides in NOx Storage Reduction Catalysts, Chem. Cat. Chem. 2, 658 (2010)
J. Jelic, K. Reuter, and R. Meyer
- In Situ X-Ray Photoelectron Spectroscopy of Model Catalysts: At the Edge of the Gap, Phys. Rev. Lett. 110, 117601 (2013)
S. Blomberg, M.J. Hoffmann, J. Gustafson, N.M. Martin, V.R. Fernandes, A. Borg, Z. Liu, R. Chang, S. Matera, K. Reuter, and E. Lundgren
(See online at https://doi.org/10.1103/PhysRevLett.110.117601) - CO Oxidation on Pd(100) vs. PdO(√5x√5)R27°: First- Principles Kinetic Phase Diagrams and Bistability Conditions, Topics Catal. 57, 159 (2014)
M.J. Hoffmann and K. Reuter
(See online at https://doi.org/10.1007/s11244-013-0172-5) - kmos: A Lattice Kinetic Monte Carlo Framework, Comp. Phys. Commun. 185, 2138 (2014)
M.J. Hoffmann, S. Matera, and K. Reuter
(See online at https://doi.org/10.1016/j.cpc.2014.04.003) - Multi-Lattice Kinetic Monte Carlo Simulations from First-Principles: Reduction of the Pd(100) Surface Oxide by CO, ACS Catal.
M.J. Hoffmann, M. Scheffler, and K. Reuter
(See online at https://doi.org/10.1021/cs501352t)
