Role of Spin Polarization and Dynamic Correlation in Singlet–Triplet Gap Inversion of Heptazine Derivatives

0576888 - ÚFCH JH 2024 RIV US eng J - Článek v odborném periodiku
Drwal, D. - Matoušek, Mikuláš - Golub, Pavlo - Tucholska, A. - Hapka, M. - Brabec, Jiří - Veis, Libor - Pernal, K.
Role of Spin Polarization and Dynamic Correlation in Singlet–Triplet Gap Inversion of Heptazine Derivatives.
Journal of Chemical Theory and Computation. Roč. 19, č. 21 (2023), s. 7606-7616. ISSN 1549-9618. E-ISSN 1549-9626
Grant CEP: GA ČR GF23-04302L
Výzkumná infrastruktura: e-INFRA CZ II - 90254
Institucionální podpora: RVO:61388955
Klíčová slova: Energy * Determinants * Quantum mechanics
Obor OECD: Physical chemistry
Impakt faktor: 5.5, rok: 2022
Způsob publikování: Open access

The new generation of proposed light-emitting molecules for organic light-emitting diodes (OLEDs) has raised considerable research interest due to its exceptional feature─a negative singlet–triplet (ST) gap violating Hund’s multiplicity rule in the excited S1 and T1 states. We investigate the role of spin polarization in the mechanism of ST gap inversion. Spin polarization is associated with doubly excited determinants of certain types, whose presence in the wave function expansion favors the energy of the singlet state more than that of the triplet. Using a perturbation theory-based model for spin polarization, we propose a simple descriptor for prescreening of candidate molecules with negative ST gaps and prove its usefulness for heptazine-type molecules. Numerical results show that the quantitative effect of spin polarization decreases linearly with the increasing highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) exchange integral. Comparison of single- and multireference coupled-cluster predictions of ST gaps shows that the former methods provide good accuracy by correctly balancing the effects of doubly excited determinants and dynamic correlation. We also show that accurate ST gaps may be obtained using a complete active space model supplemented with dynamic correlation from multireference adiabatic connection theory.
Trvalý link: https://hdl.handle.net/11104/0346286