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An improved path-integral method for golden-rule rates
Joseph E Lawrence1, David E Manolopoulos1
1Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
The Journal of Chemical Physics
|October 23, 2020
Summary
We developed a modified quantum transition state theory to accurately calculate reaction rates, including tunneling and zero-point energy effects. This new method overcomes limitations of previous approaches, ensuring reliable predictions for complex chemical systems.
Area of Science:
- Chemical Physics
- Quantum Chemistry
- Theoretical Chemistry
Background:
- Calculating reaction rates is crucial in chemistry.
- Existing methods like golden-rule quantum transition state theory (GR-QTST) have limitations.
- These limitations include size inconsistency and potential for unbounded errors.
Purpose of the Study:
- To present a modified GR-QTST method for accurate reaction rate calculations.
- To address the size inconsistency issue of the original GR-QTST.
- To accurately capture tunneling and zero-point energy effects.
Main Methods:
- Modification of the golden-rule quantum transition state theory (GR-QTST).
- Utilizing path-integral sampling in a constrained ensemble.
- Employing a novel constraint functional for improved accuracy and consistency.
Main Results:
- The modified method shows accuracy comparable to GR-QTST in one-dimensional models.
- It accurately predicts quantum rates for a multidimensional spin-boson model.
- GR-QTST fails for complex spectral densities, whereas the modified method succeeds.
Conclusions:
- The modified method reliably calculates reaction rates in condensed phase systems.
- It accurately predicts rates in the Marcus inverted regime without analytic continuation.
- This approach offers a robust alternative for quantum rate calculations.
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