Spin-Vibronic Dynamics in Open-Shell Systems beyond the Spin Hamiltonian Formalism

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Molecular Dynamics

Background:

• Vibronic coupling significantly impacts molecular processes, including photochemistry and spin relaxation.
• Simulations of vibronic coupling are well-established for organic compounds but limited for open-shell systems like transition metal and lanthanide complexes.

Purpose of the Study:

• To develop a numerical strategy for differentiating the molecular electronic Hamiltonian within multireference ab initio methods, incorporating spin-orbit coupling.
• To formulate open quantum system dynamics for predicting electron density matrix evolution under Markovian phonon bath influence up to fourth-order perturbation theory.

Main Methods:

• Derivation of a numerical strategy for differentiating the molecular electronic Hamiltonian.
• Formulation of open quantum system dynamics using fourth-order perturbation theory.
• Application to Cobalt(II) and Dysprosium(III) complexes.

Main Results:

• Successful application of the developed method to Co(II) and Dy(III) complexes.
• Validation of the computational strategy against effective spin Hamiltonian methods.
• Demonstration of long spin relaxation times in the studied complexes.

Conclusions:

• The study provides insights into the nature of vibronic coupling and the role of electronic excited states in spin relaxation.
• Highlights the necessity of advanced computational chemistry for accurate quantification of these phenomena.
• Establishes a validated computational approach for open-shell systems.