Electron Dynamics in Molecular Elementary Processes and Chemical Reactions

• Published in: Bulletin of the Chemical Society of Japan 2021, Vol.94 (4), p.1421-1477
• Main Author: Takatsuka, Kazuo
• Format: Article
• Language: English
• Subjects: Biomolecules; Born-Oppenheimer approximation; Breakdown; Broken symmetry; Chemical bonds; Chemical reactions; Chemistry; Dynamics; Electron states; Electrons; Organic compounds; Potential energy; Quantum chemistry; Reaction mechanisms; Separation; Water splitting; Wave packets
• ISSN: 0009-2673; 1348-0634
• DOI: 10.1246/bcsj.20200388

This account places a particular emphasis on recent progress in the theory and its applications of nonadiabatic electron dynamics in chemical science. After a brief description of the fundamental relevance of the breakdown of the Born-Oppenheimer approximation, we show examples of our extensive and systematic application of electron dynamics to highlight the significance and necessity of beyond-Born-Oppenheimer chemistry. The chemical subjects presented herewith cover (1) characteristic phenomena arising from nonadiabatic dynamics, (2) flow of electrons during chemical reactions and ionization dynamics, (3) symmetry breaking and its possible control in chemical reactions emerging from multi-dimensional nonadiabatic interactions, a special example which can cause possible breakdown of molecular mirror symmetry, (4) physical mechanism of charge separation in organic compounds and biomolecules, (5) essential roles of charge separation and elementary chemical reaction mechanisms in catalytic cycles of Mn oxo complexes up to Mn4CaO5 in water splitting dynamics (2H2O → 4H+ + 4e− + O2), (6) chemical bonds and huge electronic state fluctuation in densely quasi-degenerate electronic manifolds, which make chemistry without the notion of potential energy surfaces, and so on. All these materials and issues have been chosen because they are not directly resolved by the method of energetics based on time-independent quantum chemistry. We thus have been exploring, developing, and cultivating a new chemical realm beyond the Born-Oppenheimer paradigm. This account is closed with a scope about the theory of simultaneous electronic and nuclear quantum wavepacket dynamics.