Nonadiabatic Quantum Dynamics with Frozen-Width Gaussians.

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Physics

Background:

• Simulating quantum nonadiabatic dynamics is crucial for understanding chemical reactions.
• Traditional methods face challenges with large systems due to the
• curse of dimensionality
• .

Purpose of the Study:

• To review techniques for simulating quantum nonadiabatic dynamics using frozen-width moving Gaussian basis functions.
• To discuss strategies for handling multiple electronic states and expanding wave function representations.
• To explore extensions for open quantum systems.

Main Methods:

• Frozen-width moving Gaussian basis functions for nuclear wave function representation.
• On-the-fly electronic structure calculations near Gaussian centers.
• Comparison of adiabatic, diabatic, and moving crude adiabatic (MCA) representations.
• Spawning and cloning protocols for wave function expansion.
• Analysis of equations of motion and energy conservation.
• Application of the Nonstochastic Open System Schrödinger Equation (NOSSE) for open systems.

Main Results:

• Moving Gaussian basis functions offer a path to overcome the curse of dimensionality in large systems.
• The choice of electronic state representation significantly impacts the dynamics' formulation.
• Spawning and cloning are effective protocols for managing wave function complexity.
• Different equations of motion have implications for energy conservation.
• The NOSSE framework extends these methods to open quantum systems.

Conclusions:

• Moving basis approaches provide efficient methods for quantum nonadiabatic dynamics.
• Careful consideration of electronic states, wave function expansion, and open system dynamics is essential for accurate simulations.
• These techniques are vital for advancing the understanding of complex molecular processes.