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Insights into the Electronic Dynamics in Chemical Reactions

2004; American Chemical Society; Volume: 108; Issue: 5 Linguagem: Inglês

10.1021/jp036572y

1520-5215

Daniel Aktah, Daniele Passerone, Michele Parrinello,

Molecular Junctions and Nanostructures

We study with an ab initio molecular dynamics method the bond-breaking and bond-forming processes in chemical reactions. To obtain reactive trajectories, we use a newly developed method based on the optimization of a suitably defined action. The Hellmann−Feynman forces, which are needed to optimize the action, are calculated within density-functional theory. We contrast a concerted [4+2] cycloaddition of cyclopentadiene and ethylene with the nonconcerted [2+2] cycloaddition of two ethylene molecules. We find that the duration of the bond-breaking and bond-forming processes due to the nuclear motion is ∼100 fs. Moreover the electronic delocalization, as well as the HOMO−LUMO energy gap during the two reactions, allows us to distinguish clearly between the concerted and the nonconcerted mechanism.