Electronically nonadiabatic wave packet propagation using frozen Gaussian scattering.

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Chemical Dynamics

Background:

• Nonadiabatic processes are crucial in chemical reactions and spectroscopy.
• Accurate simulation of these processes requires advanced theoretical methods.
• Existing methods often face computational limitations.

Purpose of the Study:

• To develop an efficient and accurate computational approach for treating nonadiabatic dynamics.
• To interface adiabatic frozen Gaussian wave packet propagation with trajectory surface hopping.
• To enable reliable simulations of molecular systems with nonadiabatic effects.

Main Methods:

• Combining adiabatic wave packet propagation with trajectory hopping.
• Utilizing the Herman-Kluk frozen Gaussian approximation.
• Employing a compact finite difference Hessian update scheme for ab initio "on-the-fly" simulations.

Main Results:

• The developed approach successfully incorporates nonadiabatic coupling into wave packet dynamics.
• Photoabsorption spectra were accurately reproduced for benchmark models (Tully's models, pyrazine) with hundreds of trajectories.
• The method demonstrates feasibility for ab initio simulations with limited Hessian calculations per trajectory.

Conclusions:

• The new method provides an effective interface between adiabatic and surface hopping techniques.
• It offers a computationally efficient way to study nonadiabatic processes.
• The approach is accurate and reliable for simulating molecular spectra and dynamics.