On the single-Hessian Gaussian wavepacket dynamics.

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Spectroscopy

Background:

• Heller's local harmonic Gaussian wavepacket dynamics (GWD) is computationally intensive.
• Approximating vibronic spectra requires accurate molecular dynamics simulations.

Purpose of the Study:

• To introduce and validate a computationally efficient single-Hessian GWD method.
• To provide a symplectic derivation for single-Hessian GWD.
• To demonstrate its accuracy and efficiency compared to existing methods.

Main Methods:

• Developed a new symplectic derivation for single-Hessian GWD.
• Implemented high-order time-stepping geometric integrators.
• Performed on-the-fly ab initio GWD simulations.
• Calculated photoelectron and absorption spectra.

Main Results:

• Single-Hessian GWD conserves symplectic structure and avoids energy drift.
• Achieved O(ℏ) asymptotic error, comparable to local harmonic GWD.
• High-order integrators enhanced accuracy and efficiency.
• Outperformed global harmonic models in spectral calculations.

Conclusions:

• Single-Hessian GWD is a highly accurate and efficient alternative for vibronic spectra.
• Geometric integrators further improve simulation performance.
• Identified spectral features sensitive to the reference Hessian choice.