Decoherence-corrected Ehrenfest molecular dynamics on many electronic states

Area of Science:

• Computational Chemistry
• Quantum Dynamics
• Molecular Modeling

Background:

• Mixed quantum-classical methods enhance nonadiabatic molecular dynamics accuracy.
• Existing decoherence corrections require explicit potential energy surfaces for all occupied electronic states, limiting their use.
• This is impractical for systems with many occupied electronic states.

Purpose of the Study:

• To extend the recently developed collapse to a block (TAB) decoherence correction.
• To adapt TAB for efficiently handling dense manifolds of electronic states (TAB-DMS).
• To eliminate the need for explicit potential energy surface knowledge for numerous states.

Main Methods:

• Introduced a scheme for efficiently computing a limited number of approximate electronic Hamiltonian eigenstates.
• Extended the state-pairwise decoherence time definition from the original TAB method.
• Developed the TAB-DMS method for systematically improvable accuracy with more computed eigenstates.

Main Results:

• TAB-DMS accurately describes dynamics on more than two electronic states.
• The method demonstrates accuracy even with a small number of computed approximate eigenstates (four in tested models).
• TAB simulations show high accuracy when the decoherence correction is carefully parameterized, validated against exact quantum dynamics.

Conclusions:

• The adapted TAB-DMS method is practical for systems with dense electronic state manifolds.
• It offers a systematically improvable and accurate approach to nonadiabatic molecular dynamics.
• Careful parameterization of the decoherence correction is key to achieving high accuracy with TAB.