Time-Derivative Couplings for Self-Consistent Electronically Nonadiabatic Dynamics.

Area of Science:

• Quantum chemistry
• Computational chemistry
• Theoretical chemistry

Background:

• Electronically nonadiabatic dynamics methods, such as semiclassical Ehrenfest and coherent switching with decay of mixing, offer advantages but are computationally intensive.
• Their computational cost stems from the need to evaluate all components of the nonadiabatic coupling vector.

Purpose of the Study:

• To introduce a novel approximation to the self-consistent potential for nonadiabatic dynamics.
• To overcome the computational limitations of existing methods while maintaining accuracy.

Main Methods:

• The new approximation utilizes time-derivative couplings derived from overlap integrals of electronic wave functions.
• These couplings approximate the nonadiabatic coupling terms within the equations of motion.

Main Results:

• Numerical tests on ethylene demonstrate minimal loss of accuracy in ensemble-averaged results.
• The proposed method significantly enhances the efficiency of direct dynamics calculations.

Conclusions:

• This approximation makes direct dynamics calculations with self-consistent potentials more feasible for complex systems.
• It potentially lowers the computational cost, making previously prohibitive calculations practically affordable.