Benchmark Performance of Global Switching versus Local Switching for Trajectory Surface Hopping Molecular Dynamics...

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Photochemistry

Background:

• Nonadiabatic molecular dynamics (NAMD) simulations are crucial for understanding photochemical processes.
• Traditional surface hopping methods, like Tully's fewest switches, rely on calculating nonadiabatic coupling vectors, which is computationally expensive.
• A novel global switching algorithm eliminates the need for these calculations, offering potential computational savings.

Purpose of the Study:

• To extensively compare the accuracy of a newly developed global switching algorithm against the conventional Tully's fewest switches method in NAMD.
• To validate the global switching algorithm for simulating complex photochemical reactions like azobenzene photoisomerization.
• To assess the applicability of the global switching method for larger systems where nonadiabatic coupling is difficult to compute.

Main Methods:

• On-the-fly trajectory surface hopping molecular dynamics simulations were performed.
• A newly developed global switching algorithm was implemented in the Newton-X program package.
• Simulations focused on cis-to-trans and trans-to-cis azobenzene photoisomerization at the OM2/MRCI level, using 800 and 600 trajectories, respectively.

Main Results:

• Excellent agreement was observed between the global switching algorithm and Tully's fewest switches method.
• The comparison included averaged quantities (quantum yields, lifetimes) and detailed product distributions.
• Detailed analyses of hopping spot and direction distributions at conical intersections also showed strong concordance.

Conclusions:

• The global switching algorithm demonstrates high accuracy comparable to conventional methods for NAMD.
• This simplified approach significantly reduces computational costs without sacrificing accuracy.
• The global switching method is a viable and efficient tool for simulating excited-state molecular dynamics in larger, complex chemical systems.