Insights into the Electronic Dynamics in Chemical Reactions

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 108; no. 5; pp. 848 - 854
• Main Authors: Aktah, Daniel, Passerone, Daniele, Parrinello, Michele
• Format: Journal Article
• Language: English
• Published: American Chemical Society 05.02.2004
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp036572y

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.