Spin-Orbit Couplings of Open-Shell Systems with Restricted Active Space Configuration Interaction

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Molecular Physics

Background:

• Spin-orbit couplings (SOCs) are crucial for understanding molecular properties, especially in open-shell systems.
• Investigating SOCs in radicals and molecular interactions is essential for predicting chemical reactivity and spectroscopic behavior.

Purpose of the Study:

• To elucidate the origins of spin-orbit couplings (SOCs) in open-shell molecules.
• To analyze the influence of molecular geometry and intermolecular interactions on SOC magnitudes.
• To introduce a novel definition for SOC constants in molecular aggregates.

Main Methods:

• Electronic structure calculations using nonrelativistic wave functions.
• Restricted Active Space Configuration Interaction (RASCI) method for wave function determination.
• Spin-orbit mean field approximation for SOC calculations.

Main Results:

• The RASCI method is suitable for calculating SOCs in open-shell systems.
• Molecular distortions and intermolecular interactions significantly affect SOC constants.
• Established a clear relationship between SOCs and the nature of electronic states.

Conclusions:

• RASCI provides accurate SOC calculations for open-shell molecules.
• Understanding SOCs is key to interpreting electronic states and molecular behavior.
• The new SOC constant definition aids in studying molecular aggregates.