scholarly journals Impact of Van der Waals interactions on structural and nonlinear optical properties of azobenzene switches

2021 ◽  
Author(s):  
carmelo Naim ◽  
Frédéric Castet ◽  
Eduard Matito
Keyword(s):  
Density Functional ◽  
Nonlinear Optical ◽  
Van Der Waals Interactions ◽  
Dispersion Interactions ◽  
Geometrical Structures ◽  
Hartree Fock ◽  
Meta Position ◽  
Good Account ◽  
London Dispersion ◽  
Azobenzene Derivatives

<div> <div> <div> <p>The geometrical structures, relative Z-E energies, and second-order nonlinear responses of a collection of azobenzene molecules symmetrically substituted in meta- position with functional groups of different bulkiness are investigated using various ab initio and DFT levels of approximation. We show that RI-MP2 and RI-CC2 approximations provide very similar geometries and relative energies and evidence that London dispersion interactions existing between bulky meta-substituents stabilize the Z con- former. The !B97-X-D exchange-correlation functional provides an accurate description of these effects and gives a good account of the nonlinear optical response of the molecules. We show that density functional approximations should include no less than 50% of Hartree-Fock exchange to provide accurate hyperpolarizabilities. A property-structure analysis of the azobenzene derivatives reveals that the main contribution to the first hyperpolarizability comes from the azo bond, but phenyl meso-substituents can enhance it.</p> </div> </div> </div>

scholarly journals Impact of Van der Waals interactions on structural and nonlinear optical properties of azobenzene switches

2021 ◽  
Author(s):  
carmelo Naim ◽  
Frédéric Castet ◽  
Eduard Matito
Keyword(s):  
Density Functional ◽  
Nonlinear Optical ◽  
Van Der Waals Interactions ◽  
Dispersion Interactions ◽  
Geometrical Structures ◽  
Hartree Fock ◽  
Meta Position ◽  
Good Account ◽  
London Dispersion ◽  
Azobenzene Derivatives

<div> <div> <div> <p>The geometrical structures, relative Z-E energies, and second-order nonlinear responses of a collection of azobenzene molecules symmetrically substituted in meta- position with functional groups of different bulkiness are investigated using various ab initio and DFT levels of approximation. We show that RI-MP2 and RI-CC2 approximations provide very similar geometries and relative energies and evidence that London dispersion interactions existing between bulky meta-substituents stabilize the Z con- former. The !B97-X-D exchange-correlation functional provides an accurate description of these effects and gives a good account of the nonlinear optical response of the molecules. We show that density functional approximations should include no less than 50% of Hartree-Fock exchange to provide accurate hyperpolarizabilities. A property-structure analysis of the azobenzene derivatives reveals that the main contribution to the first hyperpolarizability comes from the azo bond, but phenyl meso-substituents can enhance it.</p> </div> </div> </div>

Impact of Van der Waals interactions on structural and nonlinear optical properties of azobenzene switches

2021 ◽  
Author(s):  
Carmelo Naim ◽  
Frederic Castet ◽  
Eduard Matito
Keyword(s):  
Optical Properties ◽  
Functional Groups ◽  
Nonlinear Optical ◽  
Van Der Waals ◽  
Second Order ◽  
Nonlinear Optical Properties ◽  
Van Der Waals Interactions ◽  
Geometrical Structures ◽  
Meta Position ◽  
Nonlinear Responses

The geometrical structures, relative Z-E energies, and second-order nonlinear responses of a collection of azobenzene molecules symmetrically substituted in meta-position with functional groups of different bulkiness are investigated using various...

scholarly journals Optical Properties and van der Waals-London Dispersion Interactions in Inorganic and Biomolecular Assemblies

2014 ◽  
Vol 1619 ◽  
Author(s):  
Daniel M. Dryden ◽  
Yingfang Ma ◽  
Jacob Schimelman ◽  
Diana Acosta ◽  
Lijia Liu ◽  
...  
Keyword(s):  
Optical Properties ◽  
Spectroscopic Ellipsometry ◽  
Density Functional ◽  
Type I Collagen ◽  
Strong Dependence ◽  
Van Der Waals ◽  
Fundamental Absorption Edge ◽  
Type I ◽  
Dispersion Interactions ◽  
London Dispersion

ABSTRACTThe optical properties and electronic structure of AlPO4, SiO2, Type I collagen, and DNA were examined to gain insight into the van der Waals-London dispersion behavior of these materials. Interband optical properties of AlPO4 and SiO2 were derived from vacuum ultraviolet spectroscopy and spectroscopic ellipsometry, and showed a strong dependence on the crystals’ constituent tetrahedral units, with strong implications for the role of phosphate groups in biological materials. The UV-Vis decadic molar absorption of four DNA oligonucleotides was measured, and showed a strong dependence on composition and stacking sequence. A film of Type I collagen was studied using spectroscopic ellipsometry, and showed a characteristic shoulder in the fundamental absorption edge at 6.05 eV. Ab initio calculations based on density functional theory corroborated the experimental results and provided further insights into the electronic structures, interband transitions and vdW-Ld interaction potentials for these materials.

scholarly journals Неэмпирические расчеты структуры и устойчивости нанотрубок на основе монохалькогенидов галлия

2020 ◽  
Vol 62 (6) ◽  
pp. 908
Author(s):  
В.В. Карпов ◽  
А.В. Бандура ◽  
Р.А. Эварестов
Keyword(s):  
Strain Energy ◽  
Density Functional ◽  
Density Functional Method ◽  
Computer Code ◽  
Functional Method ◽  
Dispersion Interactions ◽  
Hartree Fock ◽  
Armchair Nanotubes ◽  
Different Diameters ◽  
First Time

For the first time first-principles calculations were performed to get the dependences of strain energy and band gap of achiral nanotubes obtained by rolling up monolayers of gallium (II) sulfide and selenide. The hybrid density functional method (with 13% of the Hartree-Fock exchange) within the CRYSTAL17 computer code was used. The empirical Grimme correction was applied to describe the dispersion interactions between layers accurately. As a result of simulations of nanotubes with different chirality and different diameters, the minimum diameters of the stable single-walled nanotubes were determined, which retain the continuity of the chemical bonds on the outer nanotube surface. It was shown that the strain energy dependence on a diameter obeys a classical law of inverse squares and is the same for «zigzag» and «armchair» nanotubes.

Static- and frequency-dependent NLO properties of dithienothiophene and thienothiophene bridges — A computational investigation

2020 ◽  
Vol 19 (05) ◽  
pp. 2050018
Author(s):  
Sagar B. Yadav ◽  
Nagaiyan Sekar
Keyword(s):  
Density Functional ◽  
Nonlinear Optical ◽  
Chemical Reactivity ◽  
Second Order ◽  
Basis Sets ◽  
Frequency Dependent ◽  
Nlo Properties ◽  
Reactivity Descriptors ◽  
Hartree Fock ◽  
Perturbation Potential

We have explored detailed linear and nonlinear optical properties of push-pull systems bearing thienothiophene and dithienothiophene spacers. By using density functional theory (DFT), frequency-dependent strategies were applied to examine the polarizability ([Formula: see text] and hyperpolarizability ([Formula: see text] and [Formula: see text]. The set of global and range-separated hybrid functionals with different Hartree–Fock (HF) exchange percentage at two basis sets cc-pVDZ and cc-pVTZ were used to evaluate the nonlinear optical (NLO) properties. The observed trends in the absorption maxima supported by perturbation potential analysis; as the absorption maxima increases, the respective amplitude potential decreases. For the investigated compounds, [Formula: see text]-conjugation along with the type of substituted acceptor plays a crucial role in the enhancement of NLO properties. The presence of acceptor group and length of conjugation increase between the D and A group; the first- and second-order intrinsic hyperpolarizability increases, leads to enhanced first- as well as second-order hyperpolarizability. Bond length alternation (BLA)/bond order alteration (BOA) exploration suggested that compounds attain cyanine limit. The trends in NLO properties for investigated compounds are supported by chemical reactivity descriptors, hardness and hyperhardness analysis. The polarizability is linearly correlated with the hyperpolarizability parameters ([Formula: see text] and [Formula: see text] and shows a good regression coefficient by figures of merit analysis.

A Generally Applicable Atomic-Charge Dependent London Dispersion Correction Scheme

2019 ◽  
Author(s):  
Eike Caldeweyher ◽  
Sebastian Ehlert ◽  
Andreas Hansen ◽  
Hagen Neugebauer ◽  
Sebastian Spicher ◽  
...  
Keyword(s):  
Density Functional ◽  
Dispersion Model ◽  
Low Cost ◽  
Atomic Charge ◽  
Body Part ◽  
Dispersion Interactions ◽  
Dispersion Coefficients ◽  
Charge Dependence ◽  
London Dispersion ◽  
Dynamic Polarizabilities

The D4 model is presented for the accurate computation of London dispersion interactions in density functional theory approximations (DFT-D4) and generally for atomistic modeling methods. In this successor to the DFT-D3 model, the atomic coordination-dependent dipole polarizabilities are scaled based on atomic partial charges which can be taken from various sources. For this purpose, a new charge-dependent parameter-economic scaling function is designed. Classical charges are obtained from an atomic electronegativity equilibration procedure for which efficient analytical derivatives are developed. A numerical Casimir-Polder integration of the atom-in-molecule dynamic polarizabilities yields charge- and geometry-dependent dipole-dipole dispersion coefficients. Similar to the D3 model, the dynamic polarizabilities are pre-computed by time-dependent DFT and elements up to radon are covered. For a benchmark set of 1225 dispersion coefficients, the D4 model achieves an unprecedented accuracy with a mean relative deviation of 3.8% compared to 4.7% for D3. In addition to the two-body part, three-body effects are described by an Axilrod-Teller-Muto term. A common many-body dispersion expansion was extensively tested and an energy correction based on D4 polarizabilities is found to be advantageous for some larger systems. Becke-Johnson-type damping parameters for DFT-D4 are determined for more than 60 common functionals. For various energy benchmark sets DFT-D4 slightly outperforms DFT-D3. Especially for metal containing systems, the introduced charge dependence improves thermochemical properties. We suggest (DFT-)D4 as a physically improved and more sophisticated dispersion model in place of DFT-D3 for DFT calculations as well as for other low-cost approaches like semi-empirical models.<br><br>

A Generally Applicable Atomic-Charge Dependent London Dispersion Correction Scheme

2019 ◽  
Author(s):  
Eike Caldeweyher ◽  
Sebastian Ehlert ◽  
Andreas Hansen ◽  
Hagen Neugebauer ◽  
Sebastian Spicher ◽  
...  
Keyword(s):  
Density Functional ◽  
Dispersion Model ◽  
Low Cost ◽  
Atomic Charge ◽  
Body Part ◽  
Dispersion Interactions ◽  
Dispersion Coefficients ◽  
Charge Dependence ◽  
London Dispersion ◽  
Dynamic Polarizabilities

The D4 model is presented for the accurate computation of London dispersion interactions in density functional theory approximations (DFT-D4) and generally for atomistic modeling methods. In this successor to the DFT-D3 model, the atomic coordination-dependent dipole polarizabilities are scaled based on atomic partial charges which can be taken from various sources. For this purpose, a new charge-dependent parameter-economic scaling function is designed. Classical charges are obtained from an atomic electronegativity equilibration procedure for which efficient analytical derivatives are developed. A numerical Casimir-Polder integration of the atom-in-molecule dynamic polarizabilities yields charge- and geometry-dependent dipole-dipole dispersion coefficients. Similar to the D3 model, the dynamic polarizabilities are pre-computed by time-dependent DFT and elements up to radon are covered. For a benchmark set of 1225 dispersion coefficients, the D4 model achieves an unprecedented accuracy with a mean relative deviation of 3.8% compared to 4.7% for D3. In addition to the two-body part, three-body effects are described by an Axilrod-Teller-Muto term. A common many-body dispersion expansion was extensively tested and an energy correction based on D4 polarizabilities is found to be advantageous for some larger systems. Becke-Johnson-type damping parameters for DFT-D4 are determined for more than 60 common functionals. For various energy benchmark sets DFT-D4 slightly outperforms DFT-D3. Especially for metal containing systems, the introduced charge dependence improves thermochemical properties. We suggest (DFT-)D4 as a physically improved and more sophisticated dispersion model in place of DFT-D3 for DFT calculations as well as for other low-cost approaches like semi-empirical models.<br><br>

scholarly journals First-principles Study of Electronic and Magnetic Properties of Manganese Decorated Graphene

2016 ◽  
Vol 3 (1) ◽  
pp. 24 ◽  
Author(s):  
Bishnu Prasad Paudel ◽  
Nurapati Pantha ◽  
Narayan Prasad Adhikari
Keyword(s):  
Magnetic Properties ◽  
First Principles ◽  
Density Functional ◽  
Geometrical Structures ◽  
Functional Theory ◽  
Electronic And Magnetic Properties ◽  
Weak Binding ◽  
London Dispersion ◽  
The Stability ◽  
Quantum Espresso

<p>The functionalization of graphene by the addition of Manganese (Mn) atom to its surface has been investigated computationally by using density-functional theory (DFT) based first-principles method within DFT-D2 level of approximations. The calculations have been computed employing the Quantum ESPRESSO codes. The stability, geometrical structures, electronic and magnetic properties of pure and Mn adatom graphene systems have been studied. From the information of adsorption energies of Mn atom on the different sites of graphene, the top site is found to be the most favorable one for its adsorption. Present study finds that the London dispersion interaction plays a major role in the weak binding of Mn on graphene. The study of electronic and magnetic properties of Mn decorated graphene shows that the conduction and valence band are overlapped with finite density of states (DOS) at Fermi level. The dissimilar DOS for up and down spin calculations quantify magnetic moment as 5.48 μ<sub>B</sub> which is consistent with the previous study</p><p>Journal of Nepal Physical Society Vol.3(1) 2015: 24-34</p>

THEORETICAL STUDY OF ONE- AND TWO-PHOTON ABSORPTION PROPERTIES FOR THREE SERIES OF DIPHENYLAMINE AND DIFLUORENYLAMINE SUBSTITUTED CONJUGATED COMPOUNDS

2012 ◽  
Vol 11 (05) ◽  
pp. 1033-1056 ◽  
Author(s):  
JIN-YUN WANG ◽  
CHEN-SHENG LIN ◽  
MIN-YI ZHANG ◽  
GUO-LIANG CHAI ◽  
WEN-DAN CHENG
Keyword(s):  
Density Functional ◽  
Photon Absorption ◽  
Transition Strength ◽  
Absorption Properties ◽  
Geometrical Structures ◽  
Hartree Fock ◽  
Two Photon ◽  
Three State Model ◽  
The One ◽  
Conjugated Compounds

The one-photon (OPA) and two-photon (TPA) absorption properties of three series of symmetrically substituted quadrupolar compounds with structure of donor-π bridge-donor (D–π–D) were investigated by time-dependent density functional theory (TDDFT) based on the Hartree–Fock (HF)-optimized geometrical structures. These compounds were constructed with either phenyl or fluorenyl groups connected by vinylene unit as the central π-conjugated bridges and either diphenylamine or difluorenylamine groups as terminal electron donors. The calculated OPA spectra are dominated by two strong transitions which are attributed to the charge transfers from the donor groups to central conjugated chains. The OPA and TPA transition strength all increase with the extension of conjugated chain length in each series and the corresponding wavelength shifts red in general. The transition strength in either OPA or TPA process also increases from series one to series two or three by replacing the phenyl groups with fluorenyl groups. The intramolecular charge transfers make significant contributions to the TPA activity. According to the three-state model, the enhanced TPA activity comes from the enhancement of transition moment between states–states as conjugated chain increases.

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