scholarly journals DFT modeling of polyaniline: A computational investigation into the structure and band gap of polyaniline

2021 ◽  
Author(s):  
Kevin M Scotland ◽  
Oliver K.L. Strong ◽  
Mark Parnis ◽  
Andrew James Vreugdenhil
Keyword(s):  
Band Gap ◽  
Dft Method ◽  
Band Gaps ◽  
Basis Set ◽  
Structural Motif ◽  
Synthetic Method ◽  
Computational Investigation ◽  
Structural Units ◽  
Dft Modeling ◽  
First Time

The band gaps of three forms of polyaniline (PANI) are calculated using the DFT method with the B3LYP functional and SV(P) basis set. This marks the first time that the band gap for this polymer has been calculated using this DFT method. The calculations include an investigation of the effect of varying the benzoid-quinoid structural units, the effect of increasing oligomer length and the inclusion of Michael’s addition structures which could be residual in the polymer depending on the chosen synthetic method. All results were compared to the experimentally determined band gap of 1.5 eV as typically reported in the literature. A commonly used structural motif of alternating benzoid-quinoid units and a ratio of 0.5:0.5 benzoid: quinoid resulted in a computed band gap of 1.9 eV. Inclusion of one extra quinoid unit gave rise to a band gap of 1.3 eV. Incorporation of a Michael’s addition structure was found to dominate the band gap calculation, yielding a localized LUMO and a band gap of 1.3 eV that was insensitive to the polymer chain length and composition.

UNIFORM BENDING EFFECT ON ELECTRONIC PROPERTIES OF BORON NITRIDE NANORIBBONS: A COMPUTATIONAL INVESTIGATION

Nano LIFE ◽  
2012 ◽  
Vol 02 (02) ◽  
pp. 1240005
Author(s):  
YUNLONG LIAO ◽  
ZHONGFANG CHEN
Keyword(s):  
Boron Nitride ◽  
Band Gap ◽  
Electronic Properties ◽  
First Principles ◽  
Wide Band ◽  
Band Gaps ◽  
Computational Investigation ◽  
Wide Band Gap ◽  
Bending Effect ◽  
Boron Nitride Nanoribbons

First-principles computations were performed to investigate the uniform bending effect on the electronic properties of armchair boron nitride nanoribbons (aBNNRs) with experimentally obtained width. For both bare and hydrogen-terminated aBNNRs, the band gaps only slightly depend on the uniform bending. The insensitivity of the band structures of BNNRs to the uniform bending makes them ideal materials when their wide band gap character is desired.

Syntheses and characterization of three new sulfides with large band gaps: acentric Ba4Ga4SnS12, centric Ba12Sn4S23 and Ba7Sn3S13

2017 ◽  
Vol 46 (43) ◽  
pp. 14771-14778 ◽  
Author(s):  
Rui-Huan Duan ◽  
Peng-Fei Liu ◽  
Hua Lin ◽  
Shang-Xiong Huangfu ◽  
Li-Ming Wu
Keyword(s):  
Band Gap ◽  
Band Gaps ◽  
First Time

Three new sulfides with large band gaps, NCS Ba4Ga4SnS12, CS Ba12Sn4S23 and Ba7Sn3S13 were synthesized for the first time. Ba4Ga4SnS12 exhibits a desired balance between the band gap (2.90 eV) and the SHG intensity (34 × KDP).

scholarly journals Mechanistic Insights of BHT-Mg-Catalyzed Ethylene Phosphate’s Coordination Ring-Opening Polymerization: DFT Modeling and Experimental Data

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1105 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Andrey Shlyakhtin ◽  
Maxim Kosarev ◽  
Stanislav Karchevsky ◽  
Pavel Ivchenko
Keyword(s):  
Ring Opening ◽  
Activation Barrier ◽  
Ring Opening Polymerization ◽  
High Rate ◽  
Basis Set ◽  
Cyclic Esters ◽  
Dft Modeling ◽  
Binuclear Species ◽  
Poly Ethylene ◽  
First Time

Poly(ethylene phosphates) are promising polymers for use in biomedical applications. Catalytic ring-opening polymerization (ROP) of cyclic ethylene phosphate monomers (CEPMs) is the most effective approach for obtaining these polymers. The mechanism of coordination ROP of CEPMs remains unclear. We report, for the first time, the results of DFT modeling of CEPM ROP. In these calculations by Gaussian-09 program package with the B3PW91/DGTZVP basis set, we explored methyl ethylene phosphate (MeOEP) ROP catalyzed by dimeric and monomeric catalytic species derived from heteroleptic complex [(BHT)Mg(μ-OBn)(THF)]2 (Mg1, BHT = 2,6-di-tert-butyl-4-methylphenolate). Analysis of the reaction profiles for the binuclear and mononuclear reaction mechanisms allowed us to conclude that the ROP of MeOEP is preferentially catalyzed by mononuclear Mg complexes. This estimation was confirmed by comparative polymerization experiments using MeOEP and traditional monomers ε-caprolactone (εCL), racemic lactide (rac-LA), and l-lactide (l-LA) initiated by Mg1. ROP of MeOEP proceeds at an extremely high rate due to the substantially lower activation barrier calculated for mononuclear mechanism in comparison with that of cyclic esters that polymerize without the dissociation of BHT-Mg binuclear species. We also demonstrated the use of MeOEP as a "monomerization" agent in the synthesis of MeOEP-lactide block copolymers. Comparison of the multiple acceleration of l-LA ROP after MeOEP prepolymerization and formation of atactic PLA blocks in rac-LA polymerization with the heterotactic PLA formation during Mg1-catalyzed homopolymerization also confirmed the mononuclear nature of the polyphosphate-containing catalytic particles.

A study on K2SbF2Cl3 as a new mid-IR nonlinear optical material: new synthesis and excellent properties

2015 ◽  
Vol 3 (37) ◽  
pp. 9588-9593 ◽  
Author(s):  
Yin Huang ◽  
Xianggao Meng ◽  
Pifu Gong ◽  
Zheshuai Lin ◽  
Xingguo Chen ◽  
...  
Keyword(s):  
Band Gap ◽  
Hydrothermal Method ◽  
Nonlinear Optical ◽  
Optical Band Gap ◽  
Band Gaps ◽  
Optical Material ◽  
Nonlinear Optical Material ◽  
New Synthesis ◽  
First Time

K2SbF2Cl3 is synthesized by the hydrothermal method, and its potential is evaluated for the first time. Its powders show a phase-matchable SHG effect 4 times that of KDP. Its optical band gap is 4.01 eV which is much wider than the band gaps of the currently commercialized IR NLO crystals.

scholarly journals Comparative DFT study of triplet and singlet elementary oxidation acts of the cyclohexane and 1,3-cyclohexadiene initiated by primary interaction with 3O2 under SCF conditions

2019 ◽  
Vol 60 (11) ◽  
pp. 128-142
Author(s):  
Alexandre I. Kourdioukov ◽  
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Basis Set ◽  
Heavy Oils ◽  
Ceteris Paribus ◽  
Singlet States ◽  
Butane Mixture ◽  
Dehydrogenation Reactions ◽  
First Time ◽  
Propane Butane

The primary stages of the oxidation of model cyclohexane and 1,3-cyclohexadiene by triplet molecular oxygen and subsequent transformations involving triplet and singlet states were studied for the first time by the DFT method with the density functional B3LYP with the basis set 6-311++g(df,p). It was shown that, ceteris paribus, cyclohexane and 1,3-cyclohexadiene will be orders of magnitude more reactive compared to the activity of acyclic saturated hydrocarbons under SCF conditions when the oxidation process is initiated by the primary reaction with 3O2, which allows the propane-butane mixture to be effectively used as SCF conditions of heavy oils and use air purge to activate this process. The triplet associate complexes resulting from the oxidative cleavage of the secondary C–H bond of cyclohexane and 1,3-cyclohexadiene consist of hydrogen-bonded hydroperoxyl radical and cyclohexyl radical or 1,3-cyclohexadiene radical, respectively. These complexes can dissociate into unbound pairs of radicals, and therefore further reactions can proceed in the triplet or singlet direction. The singlet direction is characterized by hydrate-induced hydroperoxide-carbonyl transformation, as well as other hydrate-induced rearrangements. The triplet direction is characterized by the occurrence of triplet rearrangement, which in its essence is a triplet recombination of associated radicals. Associate triplet complexes can be agents of radical hydroperoxyl and alkyl activity, as well as agents of radical hydroxyl and alkoxyl activity. Most oxidative dehydrogenation reactions are absolutely real under a number of conditions, namely, they must take place under SCF conditions, as well as in the presence of an excess of SCF solvent necessary for the effective shift of thermodynamic equilibrium towards the target products in accordance with the Le Chatelier principle.

New Insights into the Nature of the Band Gap of CuGeO3 Nanoparticles: Synthesis, Electronic Structure, and Optical and Photocatalytic Properties

2019 ◽  
Author(s):  
Victor Y. Suzuki ◽  
Luís Henrique Cardozo Amorin ◽  
Natália H. de Paula ◽  
Anderson R. Albuquerque ◽  
Julio Ricardo Sambrano ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
Material Design ◽  
Photocatalytic Properties ◽  
Critical Parameters ◽  
Synthetic Approach ◽  
Microwave Assisted ◽  
Theoretical Approaches ◽  
Nanoparticles Synthesis ◽  
First Time

<p>We report, for the first time, new insights into the nature of the band gap of <a>CuGeO<sub>3</sub> </a>(CGO) nanocrystals synthesized from a microwave-assisted hydrothermal method in the presence of citrate. To the best of our knowledge, this synthetic approach has the shortest reaction time and it works at the lowest temperatures reported in the literature for the preparation of these materials. The influence of the surfactant on the structural, electronic, optical, and photocatalytic properties of CGO nanocrystals is discussed by a combination of experimental and theoretical approaches, and that results elucidates the nature of the band gap of synthetized CGO nanocrystals. We believe that this particular strategy is one of the most critical parameters for the development of innovative applications and that result could shed some light on the emerging material design with entirely new properties.</p> <p><b> </b></p>

A Comprehensive Computational Study on OCH+-Rg (Rg = He, Ne, Ar, Kr, Xe) Complexes

2003 ◽  
Vol 68 (3) ◽  
pp. 489-508 ◽  
Author(s):  
Yinghong Sheng ◽  
Jerzy Leszczynski
Keyword(s):  
Computational Study ◽  
Relativistic Effects ◽  
Dft Method ◽  
Basis Set ◽  
Rare Gas ◽  
Geometrical Parameters ◽  
Minor Effect ◽  
Dissociation Energies ◽  
Equilibrium Geometries

The equilibrium geometries, harmonic vibrational frenquencies, and the dissociation energies of the OCH+-Rg (Rg = He, Ne, Ar, Kr, and Xe) complexes were calculated at the DFT, MP2, MP4, CCSD, and CCSD(T) levels of theory. In the lighter OCH+-Rg (Rg = He, Ne, Ar) rare gas complexes, the DFT and MP4 methods tend to produce longer Rg-H+ distance than the CCSD(T) level value, and the CCSD-calculated Rg-H+ bond lengths are slightly shorter. DFT method is not reliable to study weak interaction in the OCH+-He and OCH+-Ne complexes. A qualitative result can be obtained for OCH+-Ar complex by using the DFT method; however, a higher-level method using a larger basis set is required for the quantitative predictions. For heavier atom (Kr, Xe)-containing complexes, only the CCSD method predicted longer Rg-H+ distance than that obtained at the CCSD(T) level. The DFT method can be applied to obtain the semiquantitative results. The relativistic effects are expected to have minor effect on the geometrical parameters, the H+-C stretching mode, and the dissociation energy. However, the dissociation energies are sensitive to the quality of the basis set. The nature of interaction between the OCH+ ion and Rg atoms was also analyzed in terms of the interaction energy components.

scholarly journals The SN2 reaction and its relationship with the Walden inversion, the Finkelstein and Menshutkin reactions together with theoretical calculations for the Finkelstein reaction

2021 ◽  
Author(s):  
Ibon Alkorta ◽  
José Elguero
Keyword(s):  
Linear Models ◽  
Theoretical Calculations ◽  
Computational Method ◽  
Basis Set ◽  
Free Energies ◽  
Nitrogen And Phosphorus ◽  
Atom Pairs ◽  
Leaving Groups ◽  
First Time ◽  
Nitrogen Phosphorus

AbstractThis communication gives an overview of the relationships between four reactions that although related were not always perceived as such: SN2, Walden, Finkelstein, and Menshutkin. Binary interactions (SN2 & Walden, SN2 & Menshutkin, SN2 & Finkelstein, Walden & Menshutkin, Walden & Finkelstein, Menshutkin & Finkelstein) were reported. Carbon, silicon, nitrogen, and phosphorus as central atoms and fluorides, chlorides, bromides, and iodides as lateral atoms were considered. Theoretical calculations provide Gibbs free energies that were analyzed with linear models to obtain the halide contributions. The M06-2x DFT computational method and the 6-311++G(d,p) basis set have been used for all atoms except for iodine where the effective core potential def2-TZVP basis set was used. Concerning the central atom pairs, carbon/silicon vs. nitrogen/phosphorus, we reported here for the first time that the effect of valence expansion was known for Si but not for P. Concerning the lateral halogen atoms, some empirical models including the interaction between F and I as entering and leaving groups explain the Gibbs free energies.

scholarly journals The Band-Gap Studies of Short-Period CdO/MgO Superlattices

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Ewa Przeździecka ◽  
P. Strąk ◽  
A. Wierzbicka ◽  
A. Adhikari ◽  
A. Lysak ◽  
...  
Keyword(s):  
Band Gap ◽  
Layer Thickness ◽  
Energy Gap ◽  
Band Gaps ◽  
Short Period ◽  
Wide Range ◽  
Salt Structure ◽  
Short Period Superlattices ◽  
Direct Band ◽  
Sublayer Thickness

AbstractTrends in the behavior of band gaps in short-period superlattices (SLs) composed of CdO and MgO layers were analyzed experimentally and theoretically for several thicknesses of CdO sublayers. The optical properties of the SLs were investigated by means of transmittance measurements at room temperature in the wavelength range 200–700 nm. The direct band gap of {CdO/MgO} SLs were tuned from 2.6 to 6 eV by varying the thickness of CdO from 1 to 12 monolayers while maintaining the same MgO layer thickness of 4 monolayers. Obtained values of direct and indirect band gaps are higher than those theoretically calculated by an ab initio method, but follow the same trend. X-ray measurements confirmed the presence of a rock salt structure in the SLs. Two oriented structures (111 and 100) grown on c- and r-oriented sapphire substrates were obtained. The measured lattice parameters increase with CdO layer thickness, and the experimental data are in agreement with the calculated results. This new kind of SL structure may be suitable for use in visible, UV and deep UV optoelectronics, especially because the energy gap can be precisely controlled over a wide range by modulating the sublayer thickness in the superlattices.

Gap solitons supported by an optical lattice in biased photorefractive crystals having both the linear and quadratic electro-optic effect

2020 ◽  
Vol 75 (8) ◽  
pp. 749-756
Author(s):  
Aavishkar Katti ◽  
Chittaranjan P. Katti
Keyword(s):  
Band Gap ◽  
Optical Lattice ◽  
Propagation Constant ◽  
Gap Soliton ◽  
Electro Optic ◽  
Quadratic Nonlinearities ◽  
Existence And Stability ◽  
Gap Solitons ◽  
Finite Band ◽  
First Time

AbstractWe investigate the existence and stability of gap solitons supported by an optical lattice in biased photorefractive (PR) crystals having both the linear and quadratic electro-optic effect. Such PR crystals have an interesting interplay between the linear and quadratic nonlinearities. Gap solitons are predicted for the first time in such novel PR media. Taking a relevant example (PMN-0.33PT), we find that the gap solitons in the first finite bandgap are single humped, positive and symmetric solitons while those in the second finite band gap are antisymmetric and double humped. The power of the gap soliton depends upon the value of the axial propagation constant. We delineate three power regimes and study the gap soliton profiles in each region. The gap solitons in the first finite band gap are not linearly stable while those in the second finite band gap are found to be stable against small perturbations. We study their stability properties in detail throughout the finite band gaps. The interplay between the linear and quadratic electro-optic effect is studied by investigating the spatial profiles and stability of the gap solitons for different ratios of the linear and quadratic nonlinear coefficients.

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