Probing photodissociation dynamics using ring polymer molecular dynamics.

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Photochemistry

Background:

• Simulating photodissociation requires handling non-equilibrium initial conditions.
• Standard fewest switches surface hopping (FSSH) has limitations in accurately reproducing quantum dynamics for certain photochemical scenarios.
• Recent advancements have enabled ring polymer molecular dynamics (RPMD) to address non-equilibrium conditions.

Purpose of the Study:

• To assess the performance of the ring polymer molecular dynamics (RPMD) approach for simulating photodissociation.
• To evaluate the efficacy of the ring polymer surface hopping (RPSH) approach, combining RPMD with non-adiabatic dynamics.
• To compare RPSH against the standard FSSH method for photochemical simulations.

Main Methods:

• The study employs the ring polymer surface hopping (RPSH) approach, integrating RPMD with Tully's fewest switches surface hopping (FSSH) framework.
• Non-adiabatic dynamics are treated using RPSH, incorporating non-equilibrium initial conditions.
• The methodology is validated using one-dimensional photodissociation models.

Main Results:

• RPSH with non-equilibrium initial conditions accurately reproduces time-dependent dissociation probabilities.
• The method correctly models adiabatic and diabatic populations when the crossing point is below the Franck-Condon point.
• RPSH demonstrates superior accuracy over standard FSSH, particularly when the crossing point is above the Franck-Condon point.

Conclusions:

• The ring polymer surface hopping (RPSH) approach provides an efficient and accurate method for simulating photochemical dynamics.
• RPSH overcomes limitations of standard FSSH, offering a robust alternative for studying complex photochemistry.
• This work highlights the potential of RPMD-based methods in advancing the simulation of photodissociation processes.