Ab initio two-component Ehrenfest dynamics.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Molecular Dynamics

Background:

• Electron spin dynamics are crucial in molecular systems, but accurately modeling their interplay with nuclear motion remains challenging.
• Existing methods often simplify spin configurations, limiting their applicability to complex magnetic phenomena.

Purpose of the Study:

• To develop a novel ab initio two-component Ehrenfest-based mixed quantum/classical molecular dynamics method.
• To accurately describe the coupled dynamics of nuclear motion and electron spin in molecular systems.

Main Methods:

• Utilizes two-component time-dependent non-collinear density functional theory for electron propagation.
• Employs a three-time-step algorithm integrating classical nuclear motion (velocity Verlet) and quantum electronic propagation.
• Applies a nuclear-position-dependent midpoint Fock update and modified midpoint/unitary transformation for electronic dynamics.

Main Results:

• Successfully applied the method to H2 and O2 dissociation, demonstrating its capability.
• Provides a first-principles description of non-collinear magnetic material dynamics, overcoming limitations of conventional Ehrenfest dynamics.
• Accurately captures spin-state crossover, spin-rotation, and spin-flip dynamics without spin configuration constraints.

Conclusions:

• The developed method offers a robust framework for studying spin dynamics in molecular systems.
• It enables the simulation of complex spin phenomena previously inaccessible with standard approaches.
• Shows promise for future applications in molecular spintronics and nanoscale magnetic devices.