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

Abstract

In this work we perform electronic structure calculations to unravel the origin of spin–orbit couplings (SOCs) in open-shell molecules. For that, we select systems displaying di or polyradical character, e.g., trimethylene, and analyze the changes in the magnitude of SOC constants along molecular distortions of ethylene and in the presence of intermolecular interactions between open and closed-shell moieties in the O2–C2H4 system. Calculations were performed by using nonrelativistic wave functions obtained with the restricted active space configuration interaction (RASCI) method, in conjunction with a recent implementation for the calculation of SOC based on the spin–orbit mean field approximation. Our results demonstrate the suitability of RASCI in the calculation of SOCs of open-shell systems, while providing a deep understanding of the relationship between couplings and the nature of the electronic states. Moreover, we introduce a new definition of the SOC constant for the study of molecular aggregates.

MQM 2022: The 10th Triennial Conference on Molecular Quantum Mechanics

“…Using restricted active space configuration interaction (RASCI) wave functions, Rodri ́guez-Jimeńez, Carreras, and Casanova at the Donostia International Physics Center in Spain explore the origin of these couplings and introduce a new definition of the SOC constant for molecular aggregates. 32 Next, Villegas-Escobar, Hoobler, Toro-Labbe, and Schaefer at the Pontificia Universidad Catoĺica de Chile and the University of Georgia examined the reactivity of low-valent aluminyl ions toward H 2 through a series of coupled cluster calculations. 33 They found that aluminyl systems with carbonand nitrogen-based chelating centers would serve well to activate hydrogen without dimerization.…”

“…Spin–orbit coupling (SOC) in di- and polyradical species can vary considerably with molecular distortions and in the presence of intermolecular interactions. Using restricted active space configuration interaction (RASCI) wave functions, Rodríguez-Jiménez, Carreras, and Casanova at the Donostia International Physics Center in Spain explore the origin of these couplings and introduce a new definition of the SOC constant for molecular aggregates . Next, Villegas-Escobar, Hoobler, Toro-Labbé, and Schaefer at the Pontificia Universidad Católica de Chile and the University of Georgia examined the reactivity of low-valent aluminyl ions toward H 2 through a series of coupled cluster calculations .…”