Periodicity of band gaps of chiral α-graphyne nanotubes

First-principle ultrasoft pseudo potential approach of the plane wave based on density functional theory (DFT) has been used for studying the electronic characterization and optical properties of ZnO and Fe, Co doped ZnO. The results show that the doping impurities change the lattice parameters a little, but bring more changes in the electronic structures. The band gaps are broadened by doping, and the Fermi level accesses to the conduction band which will lead the system to show the character of metallic properties. The dielectric function and absorption peaks are identified and the changes compared to pure ZnO are analyzed in detail.

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Atomic packing characteristics and electronic structures of Si nanowires from density functional tight binding calculations

Superlattices and Microstructures ◽

10.1016/j.spmi.2019.106261 ◽

2019 ◽

Vol 135 ◽

pp. 106261

Author(s):

Lijun Wu ◽

Xiumin Xu ◽

Lin Zhang ◽

Yang Qi

Keyword(s):

Electronic Structures ◽

Density Functional ◽

Tight Binding ◽

Si Nanowires ◽

Atomic Packing

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Mechanism of enhanced photocatalytic activities on tungsten trioxide doped with sulfur: Dopant-type effects

Modern Physics Letters B ◽

10.1142/s0217984916503401 ◽

2016 ◽

Vol 30 (27) ◽

pp. 1650340 ◽

Cited By ~ 1

Author(s):

Dan Li ◽

Wei-Qing Huang ◽

Zhong Xie ◽

Liang Xu ◽

Yin-Cai Yang ◽

...

Keyword(s):

Electronic Structures ◽

Tungsten Trioxide ◽

Density Functional ◽

Vacancy Defect ◽

Band Gaps ◽

Vacancy Defects ◽

Density Functional Methods ◽

Functional Methods ◽

Photocatalytic Activities ◽

Different Types

The enhanced photocatalytic activity of tungsten trioxide (WO3) has been observed experimentally via doping with S element as different dopant types. Herein, a comparative study on the effect of different types of S dopant and native vacancy defects on the electronic structure and optical properties of WO3 is presented by using hybrid Heyd–Scuseria–Ernzerhof 2006 (HSE06) density functional methods. Six possible models (S[Formula: see text]–WO3, S[Formula: see text]–WO3, V[Formula: see text]–WO3, V[Formula: see text]–WO3, S[Formula: see text] + V[Formula: see text]–WO3 and S[Formula: see text] + V[Formula: see text]–WO3) based on WO3 are tentatively put forward. It is found that cationic S doping (the substitution of W by S) is more favorable than anionic S doping (replacing O with S), and both cases become easier to form as native vacancy defect is accompanied. The electronic structures of doped WO3 depend on the type of dopant: anionic S doping results into three isolated levels in the upper part of valence band, while cationic S doping only induces an effective band gap reduction, which is critical for efficient light-to-current conversion. Interestingly, the isolated states near gap of WO3 would appear as long as native vacancy defects exist. The introduced levels or reduced band gaps make the systems responsed to the visible light, even further to a range of 400–700 nm. These findings can rationalize the available experimental results and pave the way for developing WO3-based photocatalysts.

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First-Principle Study of the Electronic and Optical Properties of Ti Doped ZnS

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.430-432.173 ◽

2012 ◽

Vol 430-432 ◽

pp. 173-176 ◽

Cited By ~ 1

Author(s):

Chang Peng Chen ◽

Jian Xiong Xie ◽

Jia Fu Wang

Keyword(s):

Optical Properties ◽

Fermi Level ◽

Conduction Band ◽

Electronic Structures ◽

Density Functional ◽

Band Gaps ◽

First Principle ◽

Level Shifts ◽

Calculation Results ◽

Impurity Elements

Based on the density functional pseudopotential method, the electronic structures and the optical properties for Ti doped ZnS are investigated in detail. The calculation results indicate that the doping of Ti widens the band gap of ZnS and the Fermi level shifts upward into the conduction band. The impurity elements form new highly localized impurity energy level at the bottom of the conduction band near the Fermi level.,.Meanwhile, blue shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change of band gaps.

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Comparative density functional theory and density functional tight binding study of arginine and arginine-rich cell penetrating peptide TAT adsorption on anatase TiO2

Physical Chemistry Chemical Physics ◽

10.1039/c6cp02671k ◽

2016 ◽

Vol 18 (29) ◽

pp. 19902-19917 ◽

Cited By ~ 14

Author(s):

Wenxuan Li ◽

Konstantinos Kotsis ◽

Sergei Manzhos

Keyword(s):

Density Functional Theory ◽

Electronic Structures ◽

Density Functional ◽

Tight Binding ◽

Anatase Tio2 ◽

Binding Study ◽

Cell Penetrating Peptide ◽

Functional Theory ◽

Cell Penetrating

A comparative DFT-DFTB study of geometries and electronic structures of arginine, arginine dipeptide, and arginine-rich cell penetrating peptide TAT on the surface of TiO2.

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First-principles study of electronic structures, thermodynamic, and thermoelectric properties of the new Rattling Full Heusler compounds Ba2AgZ (Z = As, Sb, Bi)

Revista Mexicana de Física ◽

10.31349/revmexfis.67.060501 ◽

2021 ◽

Vol 67 (6 Nov-Dec) ◽

Author(s):

Kalaliz Kheira ◽

A. Chahed ◽

M. A. Boukli ◽

M. A. Khettir ◽

A. Oughilas ◽

...

Keyword(s):

Thermoelectric Properties ◽

Electronic Structures ◽

Density Functional ◽

Heusler Alloys ◽

Band Gaps ◽

Thermoelectric Device ◽

Full Potential ◽

Seebeck Coefficients ◽

Structure State ◽

Full Heusler

The ab initio calculations based on the density functional theory (DFT) using the self-consistent Full potential linearized augmented plane wave (FPLAPW) method were performed to explore the electronic structures, thermodynamic and thermoelectric properties of new rattling Full Heusler alloys Ba2AgZ (Z = As, Sb, Bi). Results showed that the AlCu2Mn-type structure state is energetically the most stable structure. The results show that the electronic property of these cubic Rattling Heusler alloys have a semiconducting behavior with indirect band gaps Eg (L-D). The predicted band gaps were found to be 0.566, 0.548 and 0.433 eV for Z = As, Sb and Bi, respectively. The thermodynamic properties comprising the thermal expansion coefficient, heat capacity, entropy and Debye temperature parameter were evaluated at various pressures from 0 to 15 GPa. Thermoelectric properties of the Ba2AgZ (Z= As, Sb, Bi) materials are additionally computed over an extensive variety of temperature and it is discovered that all compounds exhibit ultralow thermal conductivity, good Seebeck coefficients and large high power factors, thus resulting they are suitable for use in thermoelectric device applications.

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On the reticular construction concept of covalent organic frameworks

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.1.8 ◽

2010 ◽

Vol 1 ◽

pp. 60-70 ◽

Cited By ~ 86

Author(s):

Binit Lukose ◽

Agnieszka Kuc ◽

Johannes Frenzel ◽

Thomas Heine

Keyword(s):

Density Functional ◽

Tight Binding ◽

Building Blocks ◽

Band Gaps ◽

High Symmetry ◽

Covalent Organic Frameworks ◽

Aromatic Rings ◽

Densities Of States ◽

Electronic Densities ◽

Xrd Patterns

The concept of reticular chemistry is investigated to explore the applicability of the formation of Covalent Organic Frameworks (COFs) from their defined individual building blocks. Thus, we have designed, optimized and investigated a set of reported and hypothetical 2D COFs using Density Functional Theory (DFT) and the related Density Functional based tight-binding (DFTB) method. Linear, trigonal and hexagonal building blocks have been selected for designing hexagonal COF layers. High-symmetry AA and AB stackings are considered, as well as low-symmetry serrated and inclined stackings of the layers. The latter ones are only slightly modified compared to the high-symmetry forms, but show higher energetic stability. Experimental XRD patterns found in literature also support stackings with highest formation energies. All stacking forms vary in their interlayer separations and band gaps; however, their electronic densities of states (DOS) are similar and not significantly different from that of a monolayer. The band gaps are found to be in the range of 1.7–4.0 eV. COFs built of building blocks with a greater number of aromatic rings have smaller band gaps.

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Electronic Properties of Cr and Mn Doped BN Nanowires

Materials Science Forum ◽

10.4028/www.scientific.net/msf.916.69 ◽

2018 ◽

Vol 916 ◽

pp. 69-73

Author(s):

Sena Güler Özkapı ◽

Barış Özkapı ◽

Seyfettin Dalgıç

Keyword(s):

Density Functional Theory ◽

Electronic Structures ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Band Gaps ◽

Functional Theory ◽

Zinc Blende ◽

Spin Polarized ◽

Potential Applications ◽

Mn Doped

In this work, we have investigated electronic structures of pure and doped (with Cr and Mn atoms, separately) BN nanowires along [001] direction with zinc blende phase by means of density functional theory calculations. Our results show that the substitution doping of nanowires by Cr and Mn atoms decrases the band gaps of the all BN nanowires. Also, spin polarized calculations exhibit that the density of states (DOS) for spin up and spin down electrons are antisymmetric structure for both Cr and Mn doped BN nanowires. All these show that doped BN nanowire systems have potential applications in electronics and spintronics.

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Defects in crystalline PVDF: a density functional theory-density functional tight binding study

Physical Chemistry Chemical Physics ◽

10.1039/c7cp00510e ◽

2017 ◽

Vol 19 (11) ◽

pp. 7560-7567 ◽

Cited By ~ 2

Author(s):

Saeid Arabnejad ◽

Koichi Yamashita ◽

Sergei Manzhos

Keyword(s):

Density Functional Theory ◽

Electronic Structures ◽

Polyvinylidene Fluoride ◽

Density Functional ◽

Tight Binding ◽

Binding Study ◽

Vibrational Properties ◽

Functional Theory ◽

Crystalline Phases ◽

Different Types

We present a comparative density functional theory (DFT) and density functional tight binding (DFTB) study of structures, energetics, vibrational properties as well as electronic structures of the four crystalline phases of polyvinylidene fluoride (PVDF) with different types of defects.

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Vapour Pressure Isotope Eﬀect on Evaporation from Pure Organic Phases - a PIMD Approach

10.26434/chemrxiv.12003186.v1 ◽

2020 ◽

Author(s):

Luis Vasquez ◽

Agnieszka Dybala-Defratyka

Keyword(s):

Path Integral ◽

Vapour Pressure ◽

Density Functional ◽

Isotope Effects ◽

Tight Binding ◽

Decomposition Analysis ◽

Energy Decomposition Analysis ◽

Special Importance ◽

Non Covalent Interactions ◽

Covalent Interactions

Very often in order to understand physical and chemical processes taking place among several phases fractionation of naturally abundant isotopes is monitored. Its measurement can be accompanied by theoretical determination to provide a more insightful interpretation of observed phenomena. Predictions are challenging due to the complexity of the effects involved in fractionation such as solvent effects and non-covalent interactions governing the behavior of the system which results in the necessity of using large models of those systems. This is sometimes a bottleneck and limits the theoretical description to only a few methods. In this work vapour pressure isotope effects on evaporation from various organic solvents (ethanol, bromobenzene, dibromomethane, and trichloromethane) in the pure phase are estimated by combining force field or self-consistent charge density-functional tight-binding (SCC-DFTB) atomistic simulations with path integral principle. Furthermore, the recently developed Suzuki-Chin path integral is tested. In general, isotope effects are predicted qualitatively for most of the cases, however, the distinction between position-specific isotope effects observed for ethanol was only reproduced by SCC-DFTB, which indicates the importance of using non-harmonic bond approximations. Energy decomposition analysis performed using the symmetry-adapted perturbation theory (SAPT) revealed sometimes quite substantial differences in interaction energy depending on whether the studied system was treated classically or quantum mechanically. Those observed differences might be the source of different magnitudes of isotope effects predicted using these two different levels of theory which is of special importance for the systems governed by non-covalent interactions.

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