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Creating chemical-reaction movies based on automated modeling

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If you have a question about this talk, please contact Eszter Varga-Umbrich.

We study the dynamics of chemical reactions within the quasi-classical trajectory (QCT) approach using full-dimensional ab initio analytical potential energy surfaces (PESs). For automated PES development, we apply our in-house program system, Robosurfer, and a permutationally-invariant polynomial fitting procedure. My recent research involves exploring the dynamics of halogen atom ethane reactive systems, as well as the central-atom effect in ion-molecule reactions by investigating their nitrogen- and phosphorus-centered representatives. From QCT simulations we extract reaction probabilities, integral cross sections, and scattering-angle distributions, while also monitoring the post-reaction energy flow. Reaction mechanisms can be thoroughly inspected as atomic-level movies based on our numerical results obtained from millions of trajectories. We can control chemical reactivity by applying vibrational, rotational or translational excitation to the reactants, and the effect of isotope substitution can also be modeled. We have solved a 25-year-old contradiction regarding the rotational-state distribution of the HCl product in the Cl C2H6 reaction, where we finally have obtained excellent agreement with experiment. In the bimolecular nucleophilic substitution (SN2) process at nitrogen center we have identified a novel multi-inversional reaction mechanism, which undermines stereoselectivity, a key feature at carbon center. Our QCT results, supplemented with reduced-dimensional quantum dynamics calculations have supported the experimental detection of a dynamic isotope effect in the F─ + CH3I SN2 reaction. For the weakly-bound complexes of methane with F− and Ar we have developed highly-accurate PESs that are utilized in spectroscopic calculations.

This talk is part of the Lennard-Jones Centre series.

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