Surface Hopping without Momentum Jumps: A Quantum-Trajectory-Based Approach to Nonadiabatic Dynamics.

Area of Science:

• Chemical Physics
• Quantum Dynamics
• Computational Chemistry

Background:

• Simulating nonadiabatic dynamics is crucial for understanding chemical reactions.
• Existing methods like fewest-switches surface hopping (FSSH) have limitations, including artificial momentum rescaling and breakdown of probability conservation.
• Quantum effects like coherence and decoherence are challenging to capture accurately.

Purpose of the Study:

• To develop a novel, rigorous, and broadly applicable method for simulating nonadiabatic dynamics.
• To address the limitations of existing surface-hopping algorithms.
• To incorporate quantum effects more accurately into classical trajectory simulations.

Main Methods:

• Development of quantum trajectory surface hopping (QTSH), a variant of consensus surface hopping (CSH).
• Derivation of an independent trajectory limit of CSH, recovering FSSH but replacing ad hoc momentum rescaling with quantum forces.
• Modification of classical dynamics in the adiabatic representation by a quantum-state-dependent vector potential to include geometric phase effects.

Main Results:

• QTSH rigorously conserves energy without artificial momentum rescaling, avoiding FSSH's undesirable features.
• The method naturally incorporates corrections for decoherence at reduced computational cost.
• Tested on model systems, QTSH demonstrates broader applicability and a more rigorous foundation than FSSH.
• QTSH exhibits nonclassical trajectory dynamics due to quantum forces coupling classical and quantum degrees of freedom.

Conclusions:

• QTSH provides a computationally efficient yet rigorously founded surface-hopping methodology.
• The new method overcomes key limitations of FSSH, offering improved accuracy and broader applicability.
• QTSH enables more accurate simulations of chemical dynamics, including quantum effects like geometric phases and decoherence.