Nonadiabatic semiclassical dynamics in the mixed quantum-classical initial value representation

Area of Science:

• Chemical Physics
• Quantum Dynamics
• Computational Chemistry

Background:

• Accurate simulation of real-time correlation functions is crucial for understanding chemical dynamics.
• Existing semiclassical methods often struggle with electronically nonadiabatic systems, where electronic and nuclear motions are coupled.

Purpose of the Study:

• To extend the Mixed Quantum-Classical Initial Value Representation (MQC-IVR) semiclassical method to electronically nonadiabatic systems.
• To develop a consistent dynamic framework for treating coupled electronic and nuclear degrees of freedom (dofs).

Main Methods:

• Utilized the Meyer-Miller-Stock-Thoss (MMST) Hamiltonian for a unified treatment of electronic and nuclear dofs.
• Introduced the MInt algorithm, an efficient symplectic integration scheme for numerical time evolution.
• Calculated transmission probabilities through curve crossings in model two-level systems.

Main Results:

• MQC-IVR accurately reproduces quantum-limit semiclassical results, showing good agreement with exact quantum methods.
• In the classical limit, MQC-IVR results align with established methods like linearized IVR.
• Demonstrated that selective quantization of nuclear and electronic dofs improves numerical convergence without sacrificing accuracy.

Conclusions:

• The extended MQC-IVR provides a robust and versatile tool for simulating complex chemical dynamics in nonadiabatic systems.
• The MInt algorithm offers an efficient and stable numerical approach for time evolution.
• MQC-IVR's ability to selectively quantize dofs allows for optimized computational strategies.