Nudged Elastic Band barrier

For the physisorbed structures 1-1, 1-2 and 1-3, the reaction proceeds without barrier. For the cases of chemisorption, we have calculated the energy barriers for the processes that lead from 1-1 to F-l, 1-2 to F-2 and F-l to F-6, respectively. The energy barriers have been calculated by the climbing Nudged Elastic Band method72,73 where six equidistant images have been used. 

In atomic scale simulations, there is often a clear separation of timescales. The rate of rare events, e.g., chemical reactions, in a system coupled to a heat bath can be estimated by evaluating the free energy barriers for the transitions. Transition State Theory (TST) [9] is the foundation for this approach. Due to the large difference in time scale between atomic vibrations and typical thermally induced processes such as chemical reactions or diffusion, this would require immense computational power to directly simulate dynamical trajectories for a sufficient period of time to include these rare events. Identification of transition states is often the critical step in assessing rates of chemical reactions and path techniques like the nudged elastic band method is often used to identify these states [10-12,109]. 

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