Linear fractional charge behavior in density functional theory through dielectric tuning of conductor-like polarizable continuum model

Hemmingsen, L; Hervir, Oliver A. J.; Dale, Stephen G.

doi:10.1063/5.0067685

Cited by 7 publications

(5 citation statements)

References 85 publications

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“…8 Hence, the partial charges by gas-phase B3LYP calculations are also underestimated (Figure 9). As CPCM is applied with increasing dielectric constant, ε, the magnitude of partial charges on both terminals monotonically increases, agreeing with CPCM's density localization effects as reported in the literature, 13,18 as well as our analysis in Section II-A. For all four zwitterions, the cationic N-terminals and anionic C-terminals can get their B3LYP calculated partial charges recovered to the CCSD(T) reference values by an ε of about 1.2.…”

Section: Impacts Of Cpcm On Electron Densitysupporting

confidence: 89%

“…Hemminsen, Hervir and Dale demonstrated the impacts of PCM in reproducing the linear fractional charge behavior for 147 small molecules. 18 The work provides an insightful explanation of the counterintuitive density localization observed in PCM calculations and has discussed the possibility of using PCM to reduce DEs to improve the prediction of molecular properties.…”

Section: Introductionmentioning

confidence: 99%

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Impacts of Polarizable Continuum Models on the SCF Convergence and DFT Delocalization Error of Large Molecules

Ren

Liu

2022

Preprint

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Advances in algorithm developments have enabled density functional theory (DFT) description of large molecules, including whole proteins, but the self-consistent field (SCF) convergence issues often hamper practical applications. The conductor-like polarizable continuum model (CPCM), although initially introduced as an implicit solvent model, was reported to improve SCF convergence in some large molecules. However, the underlying mechanisms and applicable use cases were unclear. We investigated the impacts of CPCM on the SCF convergence of 25 peptides and found that the CPCM only effectively reduced the SCF iterations for molecules with charge separations (e.g., the zwitterionic form of peptides) but had little effect on non-charge-separated molecules. We observed that CPCM increased the HOMO-LUMO gap of both the zwitterionic and non-charge-separated molecules, but only the charge-separated molecules suffered from the vanishing HOMO-LUMO gap problem in the gas phase which is the origin of the convergence issue. We revealed CPCM’s gap-opening mechanism as the selective stabilization/destabilization of molecular orbitals (MO) based on their local electrostatic environment. Compared to level-shifting, a traditional SCF improvement technique, CPCM has superior performance because the stabilization/destabilization of MOs is consistent through SCF iterations. Finally, we examined CPCM’s impacts on DFT density delocalization error (DDE) when used as an SCF accelerator. CPCM can mitigate the DDE and reproduce the density-derived properties (e.g., dipole moments) matching high-level methods when a very low dielectric constant is used but tends to over-localize the electron density at higher dielectric constants.

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Section: Impacts Of Cpcm On Electron Densitysupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Impacts of Polarizable Continuum Models on the SCF Convergence and DFT Delocalization Error of Large Molecules

Ren

Liu

2022

Preprint

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“…In a recent review, it has been mentioned that the application of RS hybrid functionals is the most straightforward method to reduce delocalization error. Therefore, in this study, to understand the role of localization and delocalization errors in RS density functionals, fractional occupation calculations of the five molecules have been performed using cubic spline equation − as shown below normalΔ E = [ false( ε 1 + IP false) false( 1 − normalq false) + false( − IP − ε 0 false) q ] q ( 1 − q ) …”

Section: Resultsmentioning

confidence: 99%

Understanding Photophysical Properties of Molecules Relevant in Organic Semiconductor Laser Diodes from Electron Localization Function-Tuned and Solvent-Tuned Range-Separated Functionals

Rohman,

Kar

2023

J. Phys. Chem. A

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Organic semiconductor laser diodes (OSLDs) are prevalent in optoelectronics because of their sustainable energy applications. Organic molecules used in such diodes are usually large; hence, their studies are computationally challenging with high-end benchmark methods. Computational methods with reliable accuracy and efficiency are always indispensable. In the present work, we have applied our computationally inexpensive, nonempirically tuned [electron localization function (ELF*) and solvent (Sol*)] range-separated (RS) functionals to study five molecules used in OSLDs. The emission energies in three different environments [toluene, CBP (4,4′-bis(n-carbazolyl)-1,1′-biphenyl) film, and gas] have been computed with the tuned functionals and compared with the experimental emission energies. ELF* and Sol* functionals can accurately reproduce emission energies in toluene and CBP film environments. On the other hand, both ELF* and IP-tuned functionals with excited-state geometry (IP*) perform better in the gas phase. In addition, a comparative study is performed between time-dependent density functional theory and the Tamm–Dancoff approximation. Along with the emission energy, oscillator strength values have also been reported. Different IP-tuned RS parameters were obtained with the ground- and excited-state geometries. Interestingly, it has been observed that the optimally tuned RS parameter with excited-state geometry (IP*) performs better compared to that with ground-state geometries (IP). Fractional occupation calculations show that the tuned functionals exhibit less localization and delocalization error. The study envisages that ELF* and Sol* functionals can be used to design future candidates for OSLDs.

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“…In general, density functionals with minimum delocalization and localization errors can accurately compute the ground- and excited-state properties . Recently, it has been reported that the inclusion of PCM results in localization error. , Very recently, Hemmingsen et al have reported that an implicit solvent correction with a tuned dielectric constant can be applied to balance the delocalizing characteristic of the functionals. Thus, we performed an illustrative fractional occupation calculation, using the cubic spline equation, to explore the role of the delocalization and localization error in computing the excited-state properties.…”

Section: Resultsmentioning

confidence: 99%

Excited-State Properties of Some Thermally Activated Delayed Fluorescence Emitters: Quest for an Accurate and Reliable Computational Method

Rohman

Kar

2022

J. Phys. Chem. A

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Thermally activated delayed fluorescence (TADF) finds application in organic light-emitting diodes. The molecules exhibiting TADF are characterized by small singlet−triplet energy gaps that help reverse intersystem crossing. Recently, ionization potential (IP)-tuned range-separated (RS) density functionals have been well accepted for studying excited-state properties. In the present work, two efficient descriptor-based tuning schemes [electron localization function (ELF) and Sol] of RS density functionals have been used to accurately reproduce the excited-state properties of TADF emitters by performing a single self-consistent field calculation. The lowest singlet vertical excitation energies (E VA (S 1 )) and the vertical singlet−triplet energy gaps (ΔE VST ) are computed with ELF-, Sol-, and IP-tuned RS functionals (LC-BLYP, ωB97, ωB97X, and ωB97XD). Encouraging mean absolute deviations from the experimental values with ELF*-, Sol*-, and IP-tuned functionals are observed. Consistent performance of the non-empirical tuned functionals is noted in different solvent dielectrics. In addition to these, fractional occupation calculations have shown that our tuned functionals almost satisfy the energy linearity curve. Thus, ELF*and Sol*-tuned functionals are promising and reliable alternatives in computing the excited-state properties. Considering the small experimental singlet−triplet gap, we recommend ELF* to calculate E VA (S 1 ) and Sol* to calculate ΔE VST .

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Linear fractional charge behavior in density functional theory through dielectric tuning of conductor-like polarizable continuum model

Cited by 7 publications

References 85 publications

Impacts of Polarizable Continuum Models on the SCF Convergence and DFT Delocalization Error of Large Molecules

Impacts of Polarizable Continuum Models on the SCF Convergence and DFT Delocalization Error of Large Molecules

Understanding Photophysical Properties of Molecules Relevant in Organic Semiconductor Laser Diodes from Electron Localization Function-Tuned and Solvent-Tuned Range-Separated Functionals

Excited-State Properties of Some Thermally Activated Delayed Fluorescence Emitters: Quest for an Accurate and Reliable Computational Method

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