Multimode quantum dynamics with multiple Davydov D₂ trial states: Application to a 24-dimensional conical...

Area of Science:

• Quantum dynamics
• Theoretical chemistry
• Spectroscopy

Background:

• Ultrafast nonadiabatic dynamics are crucial for understanding chemical reactions and energy transfer.
• Conical intersections (CIs) are key features in molecular systems where electronic states interact, leading to rapid transitions.
• Simulating these dynamics, especially in multimode systems, presents significant computational challenges.

Purpose of the Study:

• To investigate the ultrafast nonadiabatic dynamics of a two-electronic-state, four-vibrational-mode conical intersection coupled to a finite bath.
• To evaluate the efficiency and robustness of the multiple Davydov D2 ansatz for simulating internal conversion processes.
• To establish a benchmark for testing other simulation methods, particularly surface-hopping approaches.

Main Methods:

• Employing the multiple Davydov D2 ansatz to model the system.
• Utilizing the multi-configuration time-dependent Hartree (MCTDH) method as a benchmark for comparison.
• Performing numerically accurate simulations of time-dependent diabatic and adiabatic populations and reduced probability densities.

Main Results:

• The multiple Davydov D2 ansatz provides an efficient and robust description of internal conversion at multimode CIs.
• Accurate simulations of electronic state populations and mode-specific probability densities were achieved for a 24-mode system.
• The Gaussian nature of the Davydov ansatz facilitates precise calculations.

Conclusions:

• The multiple Davydov D2 ansatz is a powerful tool for studying complex quantum dynamics.
• The method enables accurate benchmarking for advanced simulation techniques like surface-hopping.
• This work advances the understanding of energy dissipation mechanisms in molecular systems.