The Best of Both Worlds: ΔDFT Describes Multiresonance TADF Emitters with Wave-Function Accuracy at Density-Functional Cost

The Journal of Physical Chemistry Letters, Journal Year: 2025, Volume and Issue: unknown, P. 1114 - 1125

Published: Jan. 23, 2025

With their narrow-band emission, high quantum yield, and good chemical stability, multiresonance thermally activated delayed fluorescence (MR-TADF) emitters are promising materials for OLED technology. However, accurately modeling key properties, such as the singlet-triplet (ST) energy gap energy, remains challenging. While time-dependent density functional theory (TD-DFT), workhorse of computational science, suffers from fundamental issues, wave function-based coupled-cluster (CC) approaches, like approximate CC second-order (CC2), accurate but suffer cost unfavorable scaling with system size. This work demonstrates that a state-specific ΔDFT approach based on unrestricted Kohn-Sham (ΔUKS) combines best both worlds: diverse benchmark set 35 MR-TADF emitters, ΔUKS performs or better than CC2, recovering experimental ST gaps mean absolute deviation (MAD) 0.03 eV at small fraction CC2. When combined tuned range-separated LC-ωPBE functional, excellent performance extends to energies MR- donor-acceptor TADF even molecules an inverted (INVEST), rendering this jack all trades organic electronics.

Language: Английский

---

Benchmark computations of nearly degenerate singlet and triplet states of N-heterocyclic chromophores. II. Density-based methods

The Journal of Chemical Physics, Journal Year: 2025, Volume and Issue: 162(2)

Published: Jan. 8, 2025

In this paper, we demonstrate the performance of several density-based methods in predicting inversion S1 and T1 states a few N-heterocyclic triangulene based fused ring molecules (popularly known as INVEST molecules) with an eye to identify well performing but cost-effective preliminary screening method. Both conventional linear-response time-dependent density functional theory (LR-TDDFT) ΔSCF (namely maximum overlap method, square-gradient minimization restricted open-shell Kohn–Sham) are considered for excited state computations using exchange–correlation (XC) functionals from different rungs Jacob’s ladder. A well-justified systematism is observed when compared against fully internally contracted multireference configuration interaction singles doubles and/or equation motion coupled-cluster (EOM-CCSD), most important feature being capture spin-polarization presence correlation. set least mean absolute error proposed both approaches, LR-TDDFT ΔSCF, which can be more alternatives on synthesizable larger derivatives templates studied here. We have our findings extensive studies three cyclazine-based molecular templates, additional six related templates. Previous benchmark subsets were conducted domain-based local pair natural orbital-similarity transformed EOM-CCSD (STEOM-CCSD), resulted inadequate evaluation due deficiencies theory. The role exact-exchange, spin-contamination, context DFT comes forefront supports numerical XC these applications. Suitable connections drawn two exciton models, minimal physics governing interactions molecules.

Language: Английский

---

Can ΔSCF and ROKS DFT-Based Methods Predict the Inversion of the Singlet–Triplet Gap in Organic Molecules?

Journal of Chemical Theory and Computation, Journal Year: 2025, Volume and Issue: unknown

Published: March 1, 2025

Inverted singlet–triplet gap systems (INVEST) have emerged as an intriguing class of materials with potential applications emitters in Organic Light Emitting Diodes (OLEDs). Indeed, this type material exhibits a negative energy (ΔEST), i.e., inversion the lowest singlet (S1) and triplet (T1) excited states, that goes against Hund's rule. In study, ΔEST set 15 INVEST molecules has been computed within framework Restricted Open-Shell Kohn–Sham (ROKS) Delta Self-Consistent Field (ΔSCF) methods results were benchmarked wavefunction-based calculations performed at EOM-CCSD, NEVPT2, SCS-CC2 levels. We find ROKS always (and wrongly) predicts positive global hybrid, meta-GGA, long-range corrected functionals is almost functional-independent. also show only way to obtain inverted was resort double hybrid functionals. contrast, using above-mentioned functionals, ΔSCF usually gives ΔEST, although are largely functional-dependent. Overall, applying method based on PBE0 functional provides MSD MAD respect EOM-CCSD results. further driven by different degrees orbital relaxation versus state well captured calculations. As matter fact, somehow mimics involvement higher-order excitations which leads difference spatial localization α β spins, thus introduces (local) spin polarization effects sourcing ΔEST. However, care should be taken when screen behavior view their limited quantitative correlation reference molecular data basis used here.

Language: Английский

---

Universal Framework for Multiconfigurational DFT

Journal of Chemical Theory and Computation, Journal Year: 2025, Volume and Issue: unknown

Published: March 7, 2025

Strong correlation remains a significant challenge for DFT with no satisfying solutions found yet within the standard Kohn–Sham framework. Instead, decades, number of different approaches have been suggested to combine accuracy multiconfigurational methods efficiency DFT. In this article, we demonstrate that many these are or would be significantly improved by being reformulated as variants pair-density functional theory (MC-PDFT). This work presents first implementation recently proposed variational formulation MC-PDFT. It also provides time systematic comparison their across representative examples strongly correlated systems. By analyzing and formal properties, provide design guidelines inform development future functionals.

Language: Английский

---

The Role of Theoretical Calculations for INVEST Systems: Complementarity Between Theory and Experiments and Rationalization of the Results

Advanced Optical Materials, Journal Year: 2025, Volume and Issue: unknown

Published: March 5, 2025

Abstract Here, the key role played by theoretical calculations for molecules presenting an inverted singlet‐triplet excited state (e.g. S 1 and T ) energy difference, or Δ E ST < 0, whose interest has steadily raised in recent years fostered experimental advances showing negative values a collection of real‐world systems is reviewed. The evolution computational efforts from pioneering on reduced set prototypical covered, to high‐throughput virtual screenings thousands identify new molecular scaffolds tune properties other than excitation energies, describe necessary benchmarking methods done parallel along years. Overall, complementarity prompted discovery more displaying 0 values, basic design principles are rationalized thus reviewed here too, while allowing at same time find which offer reasonable trade‐off between accuracy cost.

Language: Английский

---

Impact of Structure on Excitation Energies and S₁‐T₁ Energy Gaps of Asymmetrical Systems of Interest for Inverted Singlet‐Triplet Gaps

Journal of Computational Chemistry, Journal Year: 2025, Volume and Issue: 46(8)

Published: March 26, 2025

Computational investigations of Inverted Singlet-Triplet (INVEST) emitters often rely on ADC(2) and TD-DFT excitation energies (EEs) obtained with the vertical approximation. Here, we first considered several cyclazine derivatives examine sensitivity EEs (VEEs) as well singlet-triplet gaps, ΔES1T1 to level at which ground state (S0) structure was optimized. For cyclazine, VEEs gaps from or are spread over a narrow range (< 0.064 eV) whether S0 is optimized various DFT, CCSD, RI-MP2 methods. However, for asymmetric cyclazines, depending protocol optimizing structures, not only substantially wider (up 0.75 but so 0.30 eV), leading cases where, different one obtains positive significantly negative gaps. We relate this behavior introduction significant asymmetry bond-length variations in derivatives, formed by ligand functionalization modification core. On more note, adiabatic (AEEs) display lower (7-30× less) geometry optimization protocols than their analogs. Crucially, M06-HF functional 100% non-local exchange provides closest available CCSD(T) data. show that effect exists also other frameworks (e.g., azulene, pentaazaphenalene, non-alternant polycyclic hydrocarbons) have been INVEST property, broader up 1.19 eV 0.62 eV. emitters, it therefore extremely important judiciously choose computational geometries, computing

Language: Английский

---

Enhancing the prediction of TADF emitter properties using Δ-machine learning: A hybrid semi-empirical and deep tensor neural network approach

The Journal of Chemical Physics, Journal Year: 2025, Volume and Issue: 162(14)

Published: April 8, 2025

This study presents a machine learning (ML)-augmented framework for accurately predicting excited-state properties critical to thermally activated delayed fluorescence (TADF) emitters. By integrating the computational efficiency of semi-empirical PPP+CIS theory with Δ-ML approach, model overcomes inherent limitations in key properties, including singlet (S1) and triplet (T1) energies, singlet–triplet gaps (ΔEST), oscillator strength (f). The demonstrated exceptional accuracy across datasets varying sizes diverse molecular features, notably excelling ΔEST values, negative regions relevant TADF molecules inverted S1–T1 gaps. work highlights synergy between physics-inspired models accelerating design efficient emitters, providing foundation future studies on complex systems advanced functional materials.

Language: Английский

---