Analytical Switching Algorithms for Global Trajectory Surface Hopping Molecular Dynamics Simulation.

Area of Science:

• Computational Chemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Simulating nonadiabatic dynamics in complex photochemical systems requires accurate methods for nonadiabatic switching probabilities.
• Classical trajectory-based molecular dynamics methods are suitable but need quantum mechanical formulation for switching probabilities.

Purpose of the Study:

• To analytically solve Landau-Zener and Zhu-Nakamura switching probabilities under different quantum/classical approximations.
• To compare the global switching and fewest switching algorithms in on-the-fly trajectory surface hopping molecular dynamics simulations.

Main Methods:

• Developed analytical solutions for Landau-Zener (T̂N = 0) and Zhu-Nakamura (T̂N ≠ 0) switching probabilities.
• Employed on-the-fly trajectory surface hopping molecular dynamics simulations.
• Studied cis-to-trans and trans-to-cis azobenzene photoisomerization.

Main Results:

• Both Landau-Zener and Zhu-Nakamura probabilities are exact solutions under their respective T̂N assumptions for a two-state linear curve crossing model.
• Global switching and fewest switching algorithms showed good agreement in simulations.
• Key parameters like quantum yields, lifetimes, and population decay distributions were well-reproduced by both algorithms.

Conclusions:

• The study validates the analytical solutions for switching probabilities in nonadiabatic dynamics.
• On-the-fly trajectory surface hopping molecular dynamics, employing either global or fewest switching algorithms, is effective for simulating complex photochemical processes like azobenzene photoisomerization.