Direct simulation of electron transfer using ring polymer molecular dynamics: comparison with semiclassical instanton
Artur R Menzeleev1, Nandini Ananth, Thomas F Miller
1Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
The Journal of Chemical Physics
|August 25, 2011
Summary
Ring polymer molecular dynamics (RPMD) accurately simulates electron transfer (ET) reaction dynamics and rates in normal and activationless regimes. However, RPMD struggles with the inverted regime, failing to capture the characteristic rate turnover compared to exact quantum dynamics.
Area of Science:
- Chemical Physics
- Computational Chemistry
- Reaction Dynamics
Background:
- Electron transfer (ET) is fundamental in chemistry and biology.
- Accurate simulation of ET reaction dynamics is computationally challenging.
- Existing methods like Marcus theory and semiclassical instanton theory have limitations.
Purpose of the Study:
- To analyze the accuracy of ring polymer molecular dynamics (RPMD) for simulating condensed-phase electron transfer (ET) reaction dynamics.
- To compare RPMD predictions with Marcus theory, semiclassical instanton theory, and exact quantum dynamics.
- To investigate the performance of RPMD across different thermodynamic driving force regimes.
Main Methods:
- Ring Polymer Molecular Dynamics (RPMD) simulations.
- Atomistic and system-bath representations for condensed-phase ET.
- Comparison with Marcus theory, semiclassical instanton theory, and exact quantum dynamics.
Main Results:
- RPMD accurately predicts ET reaction rates and mechanisms in the normal and activationless regimes.
- RPMD reveals solvent reorganization mechanisms consistent with Marcus theory.
- RPMD and semiclassical instanton theory fail to accurately capture ET dynamics in the inverted regime.
Conclusions:
- RPMD is a reliable method for simulating ET dynamics in the normal and activationless regimes.
- The accuracy of RPMD is linked to its treatment of statistical fluctuations and semiclassical approximations.
- Advanced quantum dynamics are necessary for accurately describing ET in the inverted regime.
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