Accurate prediction of inverted singlet-triplet excited states using self-consistent spin-opposite perturbation theory

Nhan Tri Tran; Hoang Thanh Nguyen; Lan Nguyen Tran

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arXiv · 2603.11891

Accurate prediction of inverted singlet-triplet excited states using self-consistent spin-opposite perturbation theory

Nhan Tri Tran·Hoang Thanh Nguyen·Lan Nguyen Tran

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Abstract

The violation of Hund's rule, resulting in an inverted singlet-triplet (INVEST) gap, represents a paradigm shift in photophysics with major implications for OLED technology. INVEST molecules facilitate barrierless reverse intersystem crossing, theoretically permitting 100\% internal quantum efficiency without thermal activation. However, accurately predicting negative singlet-triplet energy gaps typically demands prohibitive computational costs. In this study, we evaluate the efficacy of our recently developed one-body Møller-Plesset perturbation theory (OBMP2) and its spin-opposite variant (O2BMP2) as efficient alternatives. Benchmarking against 30 INVEST molecules reveals that O2BMP2, with appropriate spin-opposite scaling, achieves the accuracy of ADC(3) and EOM-CCSD. Furthermore, with the possibility of reducing computational complexity to $N^4$, O2BMP2 provides a robust balance of accuracy and efficiency, making it suitable for the high-throughput screening of next-generation INVEST materials.

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Nhan Tri Tran, Hoang Thanh Nguyen, Lan Nguyen Tran. 2026-03-12. Accurate prediction of inverted singlet-triplet excited states using self-consistent spin-opposite perturbation theory. https://arxiv.org/abs/2603.11891

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