title: New Approach for Investigating Reaction Dynamics and Rates with Ab Initio Calculations.
abstract: Herein, we demonstrate a convenient approach to systematically investigate chemical reaction dynamics using the metadynamics (MetaD) family of enhanced sampling methods. Using a symmetric SN2 reaction as a model system, we applied infrequent metadynamics, a theoretical framework based on acceleration factors, to quantitatively estimate the rate of reaction from biased and unbiased simulations. A systematic study of the algorithm and its application to chemical reactions was performed by sampling over 5000 independent reaction events. Additionally, we quantitatively reweighed exhaustive free-energy calculations to obtain the reaction potential-energy surface and showed that infrequent metadynamics works to effectively determine Arrhenius-like activation energies. Exact agreement with unbiased high-temperature kinetics is also shown. The feasibility of using the approach on actual ab initio molecular dynamics calculations is then presented by using Car-Parrinello MD+MetaD to sample the same reaction using only 10-20 calculations of the rare event. Owing to the ease of use and comparatively low-cost of computation, the approach has extensive potential applications for catalysis, combustion, pyrolysis, and enzymology.
authors.affiliation: Department of Chemical Engineering, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Fleming
authors.affiliation: Department of Chemistry, Columbia University , New York, New York 10027, United States.
authors.forename: Pratyush
authors.initials: P
authors.lastname: Tiwary
authors.affiliation: Department of Chemical Engineering, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Jim
authors.initials: J
authors.lastname: Pfaendtner
mesh_terms: D000465:Algorithms; D007700:Kinetics; D008956:Models, Chemical; D013816:Thermodynamics