Scale factor database for the vibration frequencies calculated in M06-2X, one of the DFT methods

Ünal, Yener; Nassif, Wassim; Özaydin, Burak Can; Sayın, Koray

doi:10.1016/j.vibspec.2020.103189

Cited by 44 publications

(31 citation statements)

References 40 publications

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“…These Δ G ° values were calculated without scaling factor and with the recommended scaling factor of 0.970 for thermochemistry calculations with M06-2X/6-311+G(d,p). 10 The results were identical among them and almost identical or very close to the Δ E values (see the Supporting Information ).…”

Section: Resultssupporting

confidence: 67%

“…When the calculations at the M06-2X level of the main conformers showed discrepancies or gave very close values for some of them, we carried out calculations with the CCSD(T)/6-311+G(d,p) method, with Gaussian 16, or obtained the free enthalpies (Gibbs free energies, G °) from the frequency calculations at the M06-2X/6-311+G(d,p) level, without using scaling factors or, when indicated, with reported scaling factors, 10 to confirm whether the energy differences among the conformers were practically maintained or not. Δ G ° values were also calculated for many exchange equilibria: G values with the CPCM method come from Spartan’20, unless otherwise indicated; those with the SMD method arise from Gaussian 16.…”

Section: Methodsmentioning

confidence: 99%

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Computational Study of the Stability of Pyrrolidine-Derived Iminium Ions: Exchange Equilibria between Iminium Ions and Carbonyl Compounds

et al. 2022

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The tendency of carbonyl compounds to form iminium ions by reaction with pyrrolidine or chiral pyrrolidine derivatives (in other words, the relative stability to hydrolysis of these iminium ions) has been computationally examined, mainly using the M06-2X/6-311+G(d,p) method. We have thus obtained the equilibrium positions for R–CH=O + CH 2 =CH–CH=N + R 2 * → R–CH=N + R 2 * + CH 2 =CH–CH=O reactions and for related exchanges. In these exchanges, there is a transfer of a secondary amine between two carbonyl compounds. Their relative energies may be used to predict which iminium species can be predominantly formed when two or more carbonyl groups are present in a reaction medium. In the catalytic Michael additions of nucleophiles to iminium ions arising from conjugated enals, dienals, and trienals, if the formation of the new Nu–C bond is favorable, the chances of amino-catalyzed reactions to efficiently proceed, with high conversions, depend on the calculated energy values for these exchange equilibria, where the iminium tetrafluoroborates of the adducts (final iminium intermediates) must be more prone to hydrolysis than the initial iminium tetrafluoroborates. The density functional theory (DFT) calculations indicate that the MacMillan catalysts and related oxazolidinones are especially suitable in this regard.

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Section: Resultssupporting

confidence: 67%

Section: Methodsmentioning

confidence: 99%

Computational Study of the Stability of Pyrrolidine-Derived Iminium Ions: Exchange Equilibria between Iminium Ions and Carbonyl Compounds

et al. 2022

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“…there is almost never a separation of the training dataset used to fit the scaling factor and the test dataset used to determine its performance. A notable and praiseworthy exception is the recent work of Ünal et al 54 ; we strongly encourage this approach in future studies calculating and evaluating harmonic frequency scaling factors.…”

Section: Best Model Chemistry According To Existing Datamentioning

confidence: 93%

“…Traditionally, scaling factor papers have unfortunately only reported performance for a training dataset rather than an independent test dataset, unsatisfactory from a data science perspective. We praise the recent work of Ünal et al 54 in dividing their benchmark set of molecules into a training (82.2% of the original data) and a test (remaining 17.8%) set and strongly recommend this approach for all future studies.…”

Section: Separation Of Training and Test Setmentioning

confidence: 99%

Meta‐analysis of uniform scaling factors for harmonic frequency calculations

Trujillo

McKemmish

2021

WIREs Comput Mol Sci

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Vibrational frequency calculations performed under the harmonic approximation are widespread across chemistry. However, it is well‐known that the calculated harmonic frequencies tend to systematically overestimate experimental fundamental frequencies; a limitation commonly overcome with multiplicative scaling factors. In practice, multiplicative scaling factors are derived for each individual model chemistry choice (i.e., a level of theory and basis set pair), where performance is judged by, for example, the root‐mean square error (RMSE) between the predicted scaled and experimental frequencies. However, despite the overwhelming number of scaling factors reported in the literature and model chemistry approximations available, there is little guidance for users on appropriate model chemistry choices for harmonic frequency calculations. Here, we compile and analyze the data for 1495 scaling factors calculated using 141 levels of theory and 109 basis sets. Our meta‐analysis of this data shows that scaling factors and RMSE approach convergence with only hybrid functionals and double‐zeta basis sets, with anharmonicity error already dominating model chemistry errors. Noting inconsistent data and the lack of independent testing, we can nevertheless conclude that a minimum error of 25 cm−1—arising from insufficiently accurate treatment of anharmonicity—is persistent regardless of the model chemistry choice. Based on the data we compiled and cautioning the need for a future systematic benchmarking study, we recommend ωB97X‐D/def2‐TZVP for most applications and B2PLYP/def2‐TZVPD for superior intensity predictions. With a smaller benchmark set, direct comparison prefers ωB97X‐D/6‐31G* to B3LYP/6‐31G*. This article is categorized under: Electronic Structure Theory > Density Functional Theory Theoretical and Physical Chemistry > Spectroscopy

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“…GaussView 5.0.8 are used to assign both observed and computed IR wavenumbers. All theoretical wavenumbers are multiplied by 0.96 (El-Sheshtawy et al 2015;Ghrib et al 2021;Ünal et al 2021) to fit with recorded ones. Both recorded and computed wavenumbers and the appropriate assignments are registered in Table 2.…”

Section: Computational Detailsmentioning

confidence: 99%

Exploring crystal, electronic, optical and NLO properties of ethyl 4-(3,4-dimethoxy phenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro pyrimidine-5-carboxylate (MTTHPC)

2021

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Both theoretical and experimental studies are briefly discussed to shed lights on crystal shape, FT-IR, electronic, and non-linear opto-response (NLO) characteristics of ethyl4-(3,4-dimethoxyphenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate (MTTHPC). Theoretical FT_IR results are in a proper concord with recorded measurements. MTTHPC has TDM (4.78 Debye) and a doublet spins that splits original FMOs into alpha(↑, 2.44 eV) and beta(↓, 1.28 eV) offsets, respectively. MTTHPC is a potential competitor for finest perovskite solar cells (MAPbI 3 /Au-nanospheres) that possess a band offset ( 3.1 eV ) with conversion-efficiency 24.84%. MTTHPC may be the next chapter for unique avalanche photodetectors (APD). MTTHPC 1st order hyperpolarizability is 14.15 * 10 −30 esu , surpass reference urea (≈ 40 urea , urea = 0.3728 * 10 −30 esu ). Briefly, MTTHPC may be admitted as the next stage in forthcoming NLO technology.

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Scale factor database for the vibration frequencies calculated in M06-2X, one of the DFT methods

Cited by 44 publications

References 40 publications

Computational Study of the Stability of Pyrrolidine-Derived Iminium Ions: Exchange Equilibria between Iminium Ions and Carbonyl Compounds

Computational Study of the Stability of Pyrrolidine-Derived Iminium Ions: Exchange Equilibria between Iminium Ions and Carbonyl Compounds

Meta‐analysis of uniform scaling factors for harmonic frequency calculations

Exploring crystal, electronic, optical and NLO properties of ethyl 4-(3,4-dimethoxy phenyl)-6-methyl-2-thioxo-1,2,3,4-tetrahydro pyrimidine-5-carboxylate (MTTHPC)

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