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Abstract
We have investigated the origin of the S1-T1 energy levels inversion for heptazine, and other N-doped π-conjugated hydrocarbons, leading thus to an unusually negative singlet-triplet energy gap ((Formula presented.)). Since this inversion might rely on substantial doubly-excited configurations to the S1 and/or T1 wavefunctions, we have systematically applied multi-configurational SA-CASSCF and SC-NEVPT2 methods, SCS-corrected CC2 and ADC(2) approaches, and linear-response TD-DFT, to analyze if the latter method could also face this challenging issue. We have also extended the study to B-doped π-conjugated systems, to see the effect of chemical composition on the results. For all the systems studied, an intricate interplay between the singlet-triplet exchange interaction, the influence of doubly-excited configurations, and the impact of dynamic correlation effects, serves to explain the (Formula presented.) values found for most of the compounds, which is not predicted by TD-DFT.
Original language | English |
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Pages (from-to) | 553-560 |
Number of pages | 8 |
Journal | ChemPhysChem |
Volume | 22 |
Issue number | 6 |
Early online date | 16 Dec 2020 |
DOIs | |
Publication status | Published - 17 Mar 2021 |
Keywords
- ab initio calculations
- electron correlation effects
- exchange interaction
- heptazine derivatives
- singlet-triplet energy gap
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Dive into the research topics of 'Singlet-Triplet Excited-State Inversion in Heptazine and Related Molecules: Assessment of TD-DFT and ab initio Methods'. Together they form a unique fingerprint.Projects
- 1 Finished
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Equipment renewal for the Consortium des Equipements de Calcul Intensif (CECI)
Bontempi, G. (PI), CHAMPAGNE, B. (CoPI), Geuzaine , C. (CoPI), RIGNANESE, G. M. (CoPI) & Lazzaroni, R. (CoPI)
1/01/22 → 31/12/23
Project: Research
Equipment
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High Performance Computing Technology Platform
Champagne, B. (Manager)
Technological Platform High Performance ComputingFacility/equipment: Technological Platform