Coherent state mapping ring polymer molecular dynamics for non-adiabatic quantum propagations

Area of Science:

• Quantum Chemistry
• Molecular Dynamics
• Computational Chemistry

Background:

• Accurately simulating quantum dynamics is crucial for understanding chemical reactions.
• Electronic non-adiabatic dynamics present significant computational challenges.
• Existing methods often struggle with explicit nuclear quantization.

Purpose of the Study:

• To introduce a new computational method, coherent-state mapping ring polymer molecular dynamics (CS-RPMD).
• To enable accurate simulation of electronic non-adiabatic dynamics with explicit nuclear quantization.
• To provide a method that correctly describes electronic Rabi oscillations.

Main Methods:

• Utilizes coherent-state mapping for electronic degrees of freedom.
• Employs ring-polymer path-integral representation for nuclear degrees of freedom.
• Uses classical equations of motion for sampling and propagation, with reweighting for quantum Boltzmann distribution recovery.

Main Results:

• The CS-RPMD Hamiltonian avoids inter-bead coupling in the state-dependent potential, correctly describing electronic Rabi oscillations.
• A special limit of CS-RPMD satisfies detailed balance and preserves an approximate quantum Boltzmann distribution.
• Numerical tests on a two-state model system demonstrate excellent agreement with exact quantum results across various electronic couplings.

Conclusions:

• CS-RPMD is a promising new method for accurately describing electronic non-adiabatic dynamics with explicit nuclear quantization.
• The method shows potential for broader applications in quantum dynamics simulations.
• CS-RPMD offers a robust approach for studying systems where quantum effects are significant.