A comparative study of different methods for calculating electronic transition rates.

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Computational physics

Background:

• Accurate calculation of electronic transition rates is crucial for understanding chemical dynamics.
• Mixed quantum-classical methods offer a computationally tractable approach to quantum dynamics.
• Existing methods like Ehrenfest and fewest switches surface-hopping have limitations.

Purpose of the Study:

• To comprehensively compare four mixed quantum-classical methods for electronic transition rates.
• To evaluate the accuracy and efficiency of nonequilibrium Fermi's golden rule.
• To identify a cost-effective and accurate alternative for quantum dynamics simulations.

Main Methods:

• Nonequilibrium Fermi's golden rule
• Mixed quantum-classical Liouville method
• Mean-field (Ehrenfest) method
• Fewest switches surface-hopping method (diabatic and adiabatic)

Main Results:

• Nonequilibrium Fermi's golden rule shows good agreement with the mixed quantum-classical Liouville method and exact quantum results under weak to moderate electronic coupling.
• The methods were tested on the Garg-Onuchic-Ambegaokar benchmark charge-transfer model across various temperatures and coupling strengths.
• Discrepancies were observed with Ehrenfest and fewest switches surface-hopping methods in certain regimes.

Conclusions:

• Nonequilibrium Fermi's golden rule is a reliable and accurate method for calculating electronic transition rates.
• It provides a computationally inexpensive alternative to more complex methods like Ehrenfest and fewest switches surface-hopping.
• This finding can guide the selection of appropriate computational methods in quantum dynamics studies.