The Ehrenfest method with fully quantum nuclear motion (Qu-Eh): Application to charge migration in radical cations

Area of Science:

• Quantum mechanics
• Computational chemistry
• Chemical dynamics

Background:

• Accurate simulation of quantum dynamics is crucial for understanding chemical reactions.
• Existing methods like variational multi-configuration Gaussian (vMCG) can be computationally intensive.
• The exact factorization method offers an alternative perspective on electron-nuclear coupling.

Purpose of the Study:

• To introduce and describe the Quantum-Ehrenfest (Qu-Eh) algorithm for quantum dynamics.
• To highlight the computational efficiency of Qu-Eh compared to vMCG.
• To explore the relationship between Qu-Eh and the exact factorization method.

Main Methods:

• Development of the Quantum-Ehrenfest (Qu-Eh) algorithm, combining Ehrenfest potential with quantum nuclear motion.
• Comparison of Qu-Eh with the single-set variational multi-configuration Gaussian (vMCG) approach.
• Application to model systems including modified bismethylene-adamantane cation, distorted allene, and HCCI+.

Main Results:

• The Qu-Eh method requires only a single quantum chemistry computation per time step.
• Demonstrated computational advantage over vMCG for electron dynamics simulations.
• Presented illustrative examples of electron-nuclear dynamics in various chemical systems.

Conclusions:

• The Qu-Eh algorithm provides an efficient and accurate approach for quantum dynamics.
• This method simplifies calculations by utilizing a single time-dependent potential surface.
• Qu-Eh offers a valuable alternative for studying complex electron-nuclear dynamics.