scholarly journals Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

scholarly journals Predicting Carbonyl Excitation Energies Efficiently Using EOM-CC Trends

2020 ◽  
Author(s):  
Keiran Rowell ◽  
Scott Kable ◽  
Meredith J. T. Jordan
Keyword(s):  
Single Point ◽  
Zero Point ◽  
Tropospheric Chemistry ◽  
Excitation Energies ◽  
Relaxation Energy ◽  
Point Energy ◽  
Vertical Excitation ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Carbonyl Species

We approach the problem of predicting excitation energies of diverse, larger (5–6 carbons) carbonyl species central to earth’s tropospheric chemistry. Triples contributions are needed for the vertical excitation energy (E<sup>vert</sup>), while EOM-CCSD//TD-DFT calculations provide acceptable estimates for the S<sub>1</sub> relaxation energy (E<sup>relax</sup>), and (TD-)DFT suffices for the S<sub>0</sub> → S<sub>1</sub> zero-point vibration energy correction (∆E<sup>ZPVE</sup>). <div><br></div><div>Perturbative triples corrections deliver E<sup>vert</sup> values close in accuracy to full iterative triples EOM-CC calculations. The error between EOM-CCSD and triples-corrected E vert values appears to be systematic and can be accounted for with scaling factors. However, saturated and α,β-unsaturated carbonyls must be treated separately. Double-hybrid S<sub>0</sub> minima can be used to calculate E<sup>vert</sup> with negligible loss in accuracy, relegating the O(N<sup>5</sup>) expense of CCSD to only single-point energy and excitation calculations. </div><div><br></div><div>This affordable protocol can be applied to all volatile carbonyl species. E<sup>0−0</sup> predictions do overestimate measured values by ∼8 kJ/mol due to a lack of triples contribution in E relax, but this overestimation is systematic and the mean unsigned error is within 4 kJ/mol once this is accounted for.</div>

Zero point corrections to vertical excitation energies

1998 ◽  
Vol 285 (3-4) ◽  
pp. 155-159 ◽  
Author(s):  
Ernest R. Davidson ◽  
Andrzej A. Jarzęcki
Keyword(s):  
Zero Point ◽  
Excitation Energies ◽  
Vertical Excitation ◽  
Vertical Excitation Energies

scholarly journals Excited States Computation of Models of Phenylalanine Protein Chains: TD-DFT and Composite CC2/TD-DFT Protocols

2022 ◽  
Vol 23 (2) ◽  
pp. 621
Author(s):  
Marine Lebel ◽  
Thibaut Very ◽  
Eric Gloaguen ◽  
Benjamin Tardivel ◽  
Michel Mons ◽  
...  
Keyword(s):  
Excited States ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Vibrational Energy ◽  
Zero Point ◽  
Quantitative Agreement ◽  
Geometrical Parameters ◽  
Excitation Energies ◽  
Dft Methods ◽  
Td Dft

The present benchmark calculations testify to the validity of time-dependent density functional theory (TD-DFT) when exploring the low-lying excited states potential energy surfaces of models of phenylalanine protein chains. Among three functionals suitable for systems exhibiting charge-transfer excited states, LC-ωPBE, CAM-B3LYP, and ωB97X-D, which were tested on a reference peptide system, we selected the ωB97X-D functional, which gave the best results compared to the approximate coupled-cluster singles and doubles (CC2) method. A quantitative agreement for both the geometrical parameters and the vibrational frequencies was obtained for the lowest singlet excited state (a ππ* state) of the series of capped peptides. In contrast, only a qualitative agreement was met for the corresponding adiabatic zero-point vibrational energy (ZPVE)-corrected excitation energies. Two composite protocols combining CC2 and DFT/TD-DFT methods were then developed to improve these calculations. Both protocols substantially reduced the error compared to CC2 and experiment, and the best of both even led to results of CC2 quality at a lower cost, thus providing a reliable alternative to this method for very large systems.

scholarly journals Are Carbon Clusters the Cause of Interstellar Diffuse Bands?

1992 ◽  
Vol 150 ◽  
pp. 139-141
Author(s):  
S P Tarafdar ◽  
K S Krishna Swamy ◽  
C. Badrinathan ◽  
D. Mathur
Keyword(s):  
Electronic Transition ◽  
Band System ◽  
Carbon Clusters ◽  
Excitation Energies ◽  
Diffuse Band ◽  
Electronic Band ◽  
Vertical Excitation ◽  
A Value ◽  
Vertical Excitation Energy ◽  
Vertical Excitation Energies

Theoretically determined vertical excitation energies of C5 and C7 molecules have been shown to agree with the strongest diffuse interstellar band at 4430Å. Several other weak diffuse bands can be identified with vibrational transitions, if 4430Å band is taken as 0-3 transition and vibrational constant have a value of 2190cm−1. The vertical excitation energy of a second electronic transition of C7 molecule agrees with diffuse band at 6177Å. This electronic band system may account for diffuse bands at 5778Å, 6660Å and other bands near them.

scholarly journals Photophysical Properties and Electronic Structure of Symmetrical Curcumin Analogues and Their BF2 Complexes, Including a Phenothiazine Substituted Derivative

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2299
Author(s):  
Emese Gál ◽  
Levente Csaba Nagy
Keyword(s):  
Theoretical Study ◽  
Photophysical Properties ◽  
Emission Spectra ◽  
Molecular Structures ◽  
Excitation Energies ◽  
Dft Methods ◽  
Conjugated Systems ◽  
Vertical Excitation ◽  
Td Dft ◽  
The One

Symmetrically substituted curcumin analogue compounds possess electron donor moieties at both ends of the conjugated systems; their difluoroboron complexes were synthesized, and their structures were fully characterized. A novel compound with enhanced photophysical properties bearing phenothiazine moieties is reported. The introduction of BF2 into the molecular structures resulted in bathochromic shifts both in the absorption and emission spectra, indicating that the π-conjugation was more extended than the one in the initial compounds. The solvatochromic effects were studied, which in case of the phenothiazinyl-curcumin BF2 complex was the most notable. Theoretical study of the investigated compounds was carried out using DFT and TD-DFT methods to evaluate the ground state geometries and vertical excitation energies.

scholarly journals Synthesis and Density Functional Theory Studies of Azirinyl and Oxiranyl Functionalized Isoindigo and (3Z,3’Z)-3,3’-(ethane-1,2-diylidene)bis(indolin-2-one) Derivatives

Molecules ◽  
2019 ◽  
Vol 24 (20) ◽  
pp. 3649
Author(s):  
Gholamhossein Khalili ◽  
Patrick McCosker ◽  
Timothy Clark ◽  
Paul Keller
Keyword(s):  
Density Functional ◽  
Functional Group ◽  
Functional Theory ◽  
Vertical Excitation ◽  
Design And Synthesis ◽  
Mild Conditions ◽  
Disubstituted Derivative ◽  
Td Dft ◽  
Vertical Excitation Energy ◽  
Homo Lumo

The design and synthesis of functionalized isoindigo compounds by reaction of isoindigo with (S)-glycidyl tosylate, epibromohydrin, 2-(bromomethyl)-1-(arylsulfonyl)aziridine, and 2-(bromomethyl)-1-(alkylsulfonyl)aziridine in the presence of MeONa proceed under mild conditions in moderate yields. (3Z,3’Z)-3,3’-(Ethane-1,2-diylidene)bis(1-(oxiran-2-ylmethyl)indolin-2-one), with an extended central olefin π-conjugated moiety was also reacted with methyl-oxiranes to give the corresponding N,N’-disubstituted derivative. Calculations with DFT and TD-DFT of hypothetical isoindigo-thiophene DA molecules with various electron withdrawing substituents, including aziridine, oxirane, nitrile, carbonyl, and sulfonate, indicated that the proximity and strength of the functional group have a significant effect on the HOMO, LUMO, vertical excitation energy, and oscillator strength of the π–π* transitions.

Quantum Chemistry Theoretical Studies on Molecular Structures of Polybutadiene

2009 ◽  
Vol 87-88 ◽  
pp. 130-133
Author(s):  
Ming Zhang ◽  
Zhi Xiong Huang ◽  
Min Xian Shi
Keyword(s):  
Molecular Weight ◽  
Quantum Chemistry ◽  
Function Theory ◽  
Single Point ◽  
Zero Point ◽  
Dft Method ◽  
Density Function Theory ◽  
Molecular Structures ◽  
Theoretical Studies ◽  
Point Energy

The Density Function Theory (DFT) method are employed to study the geometries of the polybutadiene （C4H6）n（n=3，4，5）on the base of B3LYP/6-311+G in the paper. the polybutadiene have five isomers, including Cis-1，4-polybutadiene, Trans-1, 4-polybutadiene, Isotactic1, 2-polybutadiene, Syndiotactic1，2-polybutadiene, Atactic1, 2-polybutadiene. The molecular structures of each isomer were evaluated on the basis of single point energy with zero point vibration correction. The results show that the energies of polybutadiene varied with increase of molecular weight.

scholarly journals Study on the Mechanism of the Effect of Temperature on the Decomposition Reaction of SFn (n=1-6) under Discharge Conditions

2021 ◽  
Author(s):  
Minghao Yang ◽  
Jing Yan ◽  
Mengyuan Xu ◽  
Yingsan Geng ◽  
Zhiyuan Liu ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Electron Energy ◽  
Single Point ◽  
Zero Point ◽  
Decomposition Reaction ◽  
Chemical Kinetic ◽  
Effect Of Temperature ◽  
Thermal Decomposition Mechanism ◽  
Chemical Kinetic Model ◽  
Point Energy

Abstract The study on the mechanism of the effect of temperature on the decomposition reaction of SFn (n = 1–6) under discharge conditions is very important in studying the potential fault of SF6 high voltage switch equipment and perfecting the chemical kinetic model of SFn discharge. In this paper, structural optimizations, vibrational frequency calculations, and zero-point energy calculations for the reactants and products were performed at the B3LYP/6-311 + + G(d,p) theory level. The single-point energies of all species were collected at the CCSD(T)/aug-cc-PVTZ level. The electric and thermal decomposition mechanism of SFn under discharge conditions of 298K–10000K were studied, respectively. The conclusion drawn was that in the temperature range of 298–10000K, the thermal decomposition homopolytic reaction △G began to decline from 200 kJ/mol, while the △G of the other two heterogenous reactions began to decrease from 1000 kJ/mol and 2000 kJ/mol, showing a downward trend of an almost similar slope. The electrolysis of SFn is related to the electron energy. When the electron energy is low, SFn + e→SFn− series reactions occur, and △G of R12, R20, R28, R36, R44 increases with temperature rise, while △G of R4 decreases with temperature. When the electron energy is high, one of SFn−→SFn−1− + F、SFn−→SFn−1 + F− and SFn−→SFn−1 + F + e will occur, and the reactions that occur at various temperature ranges as the temperature rises vary. When the second electron hits the SFn−, the SFn− + e→SFn−1− + F reaction will occur. The △G of this reaction slowly decreases with an increase in temperature. This study in clearer terms explains the decomposition process and mechanism of SFn at different temperatures.

scholarly journals A Theoretical Study of 5-methyl-2-isopropylphenol (Thymol) by DFT

2021 ◽  
pp. 812-830
Author(s):  
Raksha Gupta
Keyword(s):  
Population Analysis ◽  
Dft Method ◽  
Geometric Optimization ◽  
Oscillator Strengths ◽  
Basis Set ◽  
Excitation Energies ◽  
Mulliken Population ◽  
Visible Absorption ◽  
Vertical Excitation ◽  
Td Dft

Gaussian 09, RevisionA.01, software package was used for the theoretical quantum chemical calculations of 5-methyl-2-isopropylphenol. DFT/B3LYP/6-311G (d, p) basis was used to perform geometric optimization and vibrational frequency determination of the molecule. The statistical thermochemical calculations of the molecule were done at DFT/B3LYP/6-311G (d, p) basis set to calculate the standard thermodynamic functions: heat capacity (CV), entropy (S) and Enthalpy (E). Various NLO properties like total dipole moment (µ), mean linear polarizability (α), anisotropic polarizability (Δα), first order polarizability (β), and second order hyperpolarizability (γ) in terms of x, y, z components were calculated at DFT/B3LYP/6-311G (d, p) basis set for 5-methyl-2-isopropylphenol. Mulliken population analysis was also done using the same basis set. Time Dependent DFT (TD-DFT) method using the same basis set was used to compute UV-Visible absorption spectra, ECD spectra, electronic transitions, vertical excitation energies and oscillator strengths of 5-methyl-2-isopropylphenol.FMO analysis, ESP study were also done using the same basis set.

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