Single-Hessian thawed Gaussian approximation

Area of Science:

• Quantum chemistry
• Spectroscopy
• Computational physics

Background:

• On-the-fly ab initio semiclassical calculations of molecular spectra are computationally intensive.
• Existing methods like global harmonic schemes may lack accuracy for complex systems.

Purpose of the Study:

• To develop a computationally efficient approximation for ab initio semiclassical calculations.
• To reduce the computational cost of molecular spectra simulations.

Main Methods:

• Proposing the single-Hessian thawed Gaussian approximation.
• Approximating the potential energy Hessian with a constant matrix along classical trajectories.
• Comparing results with exact quantum and experimental spectra.

Main Results:

• The single-Hessian method achieves accuracy comparable to the more expensive thawed Gaussian approximation.
• It significantly outperforms global harmonic schemes.
• The method conserves energy exactly and can be mapped to a time-independent classical Hamiltonian.

Conclusions:

• The single-Hessian thawed Gaussian approximation is an effective and efficient method for molecular spectra calculations.
• It provides a good balance between accuracy and computational cost.
• This approach facilitates faster prefactor calculations in semiclassical simulations.