Velocity Rescaling in Surface Hopping Based on Atomic Contributions to Electronic Transitions

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Theoretical Spectroscopy

Background:

• Surface hopping is crucial for simulating nonadiabatic dynamics, where nuclear motion and electronic transitions occur.
• Accurate energy conservation during electronic transitions requires atomic velocity adjustments.
• Existing velocity rescaling methods have limitations like size-consistency issues or high computational cost.

Purpose of the Study:

• To develop novel velocity rescaling methods for surface hopping that improve energy conservation.
• To incorporate atomic contributions to electronic transitions into velocity adjustment schemes.
• To provide computationally efficient and accurate alternatives to traditional methods.

Main Methods:

• Introduced two new velocity rescaling methods: excitation-weighted and excitation-thresholded.
• Methods derive atomic contributions from the one-electron transition density matrix or density difference.
• Validated through excited-state dynamics simulations of fulvene and 1H-1,2,3-triazole.

Main Results:

• Excitation-weighted velocity rescaling redistributes kinetic energy based on atomic contributions to electronic transitions.
• Excitation-thresholded velocity rescaling adjusts velocities only for atoms exceeding a contribution threshold.
• Both methods were successfully validated, with excitation-weighted rescaling closely matching nonadiabatic coupling vector adjustments.

Conclusions:

• The proposed velocity rescaling methods offer accurate and efficient ways to conserve energy in surface hopping simulations.
• These methods address limitations of traditional approaches by considering atomic contributions to electronic transitions.
• The findings advance the simulation of nonadiabatic dynamics in molecular systems.