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Abstract

Kinetic models parameterized byab-initiocalculations have led to significantimprovements in understanding chemical reactions in heterogeneous catalysis. Thesestudies have been facilitated by implementations which determine steady-state cov-erages and rates of mean-field micro-kinetic models. As implemented in the open-source kinetic modeling program, CatMAP, the conventional solution strategy is touse a root-finding algorithm to determine the coverage of all intermediates throughthe steady-state expressions, constraining all coverages to be non-negative and toproperly sum to unity. Though intuitive, this root-finding strategy causes issues withconvergence to solution due to these imposed constraints. In this work, we avoidexplicitly imposing these constraints, solving the mean-field steady-state micro-kinetic model in the space ofnumber of sitesinstead of solving it in the space ofcov-erages. We transform the constrained root-finding problem to an unconstrainedleast-squares minimization problem, leading to significantly improved convergence insolving micro-kinetic models and thus enabling the efficient study of more complexcatalytic reactions.