Nuclear-electronic orbital Ehrenfest dynamics

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Chemical dynamics

Background:

• The real-time nuclear-electronic orbital (RT-NEO) method treats electrons and protons quantum mechanically.
• RT-NEO neglects the motion of other nuclei, limiting its scope in coupled nuclear-electronic dynamics.

Purpose of the Study:

• To develop a method that incorporates the dynamics of all nuclei in quantum-mechanical simulations.
• To enable a complete description of coupled nuclear-electronic dynamics and spectroscopy.

Main Methods:

• Introduced the NEO-Ehrenfest approach, combining RT-NEO with mixed quantum-classical Ehrenfest dynamics.
• Propagated electrons and quantum protons via RT-NEO within a time-dependent variational framework.
• Treated remaining nuclei classically, moving on an average electron-proton vibronic surface.

Main Results:

• Successfully incorporated non-Born-Oppenheimer effects for both electron-proton and classical nuclei-electron-proton subsystems.
• Resolved spectral features for vibrational modes involving both quantum and classical nuclei.
• Demonstrated the method's capability to study complex dynamical processes.

Conclusions:

• The NEO-Ehrenfest method is a powerful computational tool for simulating systems with coupled electronic and nuclear degrees of freedom.
• This approach provides a more complete description of nuclear-electronic dynamics and spectroscopy than previous methods.