Toward a Database of Chemically Accurate Barrier Heights for Reactions of Molecules with Metal Surfaces

Being able to calculate reaction barrier heights to within chemical accuracy (errors < 1 kcal/mol) is crucial to the accurate modeling of chemical reactions. Although accurate databases exist that can help theorists with benchmarking new electronic structure theories on gas-phase chemical reactions, no such databases exist for reactions of molecules with metal surfaces. Nonetheless, most chemicals are made in heterogeneously catalyzed processes, of which many take place over metal particles. Presently, barrier heights for molecule metal surface reactions have been determined with chemical accuracy for only two systems, that is, H-2 + Cu(111) and H-2 + Cu(100). This has been done with semiempirically determined density functionals, which were fitted through comparisons of dynamics results with molecular beam sticking probabilities. The prospects of extending the database with chemically accurate data for other molecule metal reactions, either with the use of semiempirical density functional theory or with first-principles theory, are discussed.