An accurate, non-empirical method for incorporating decoherence into Ehrenfest dynamics

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Chemical Physics

Background:

• Mixed quantum-classical methods in molecular dynamics often suffer from errors due to electronic wave function anchoring.
• Decoherence methods are crucial for mitigating these errors in Ehrenfest and surface hopping dynamics.
• Current decoherence methods frequently rely on empirically fitted parameters, limiting their accuracy.

Purpose of the Study:

• To refine the "collapse to a block" (TAB) scheme for incorporating decoherence into Ehrenfest dynamics.
• To develop a parameter-free decoherence approach for mixed quantum-classical simulations.
• To improve the accuracy and reliability of nonadiabatic molecular dynamics simulations.

Main Methods:

• The refined TAB scheme approximates population dynamics history and models coherence decay as Gaussian.
• This approach utilizes parameters derivable from first-principles calculations.
• A linear least-squares algorithm is introduced for robust determination of collapse probabilities.

Main Results:

• The refined TAB method demonstrates excellent agreement with numerically exact simulations for one-dimensional models.
• The new scheme avoids empirical fitting, relying on physically meaningful parameters.
• The Gaussian coherence decay and history approximation improve the treatment of decoherence.

Conclusions:

• The refined TAB scheme provides an accurate and parameter-free method for decoherence in Ehrenfest dynamics.
• This advancement enhances the reliability of mixed quantum-classical nonadiabatic molecular dynamics.
• The developed techniques offer a more robust approach to simulating quantum effects in chemical processes.