A unified framework of mixed quantum-classical dynamics with trajectory branching

Area of Science:

• Quantum mechanics and computational chemistry
• Theoretical chemistry and chemical physics
• Methodology development in computational dynamics

Background:

• Mixed quantum-classical dynamics methods like trajectory surface hopping and Ehrenfest mean field are standard for simulating nonadiabatic processes.
• Existing methods have limitations in accurately capturing complex quantum effects during dynamics.
• Recent advancements include branching-corrected surface hopping and branching-corrected mean field methods.

Purpose of the Study:

• To present a unified framework for mixed quantum-classical dynamics by combining surface hopping and mean field approaches with branching correction.
• To establish the reliability and flexibility of this new unified method (BCSHMF) across various scattering models.
• To demonstrate the essential role of trajectory branching in accurately describing nonadiabatic dynamics within a mixed quantum-classical context.

Main Methods:

• Development of the mixed surface hopping and mean field with branching correction (BCSHMF) framework.
• Benchmarking BCSHMF against thousands of diverse three-level and four-level scattering models.
• Comparison with exact quantum dynamics to validate the accuracy of BCSHMF.

Main Results:

• BCSHMF closely reproduces exact quantum dynamics in standard scattering models.
• The unified BCSHMF framework demonstrates high reliability and flexibility.
• Thousands of diverse scattering models were used for comprehensive benchmarking.

Conclusions:

• Surface hopping and mean field methods are fundamentally compatible within a unified framework.
• Trajectory branching is an essential component for accurate mixed quantum-classical descriptions of nonadiabatic dynamics.
• BCSHMF offers a robust and versatile approach for simulating complex nonadiabatic processes.