scholarly journals Electronic Transitions, Inter- and Intra-Bond Interactions of an Azabicycle Single Crystal using DFT

2021 ◽  
Vol 33 (10) ◽  
pp. 2365-2372
Author(s):  
J. Dineshkumar ◽  
S. Subashchandrabose ◽  
S. Niaz ◽  
P. Parthiban
Keyword(s):  
Functional Groups ◽  
Density Of States ◽  
Electronic Transitions ◽  
Partial Density ◽  
Electronic Charge ◽  
Total Density ◽  
X Ray Diffraction ◽  
Mannich Condensation ◽  
Td Dft ◽  
Total Density Of States

2,4-Diphenyl-3-azabicyclo[3.3.1]nonan-9-one O-benzyloxime (ABN-OBn) was synthesized by modified Mannich condensation, purified by recrystallization and single crystals were grown by slow evaporation from ethanol. The empirical formula of the molecule is C27H28N2O as witnessed by HRMS, elemental analysis and the X-ray diffraction. The crystal belongs to triclinic system (α = 73.640, β = 78.505, γ = 87.078) with P-1 space group. The electronic excited states of ABN-OBn have been calculated using TD-DFT/B3LYP/6-31G(d,p) level of theory, in order to investigate the electronic transitions within the molecule. Frontier molecular orbitals (FMOs) of ABN-OBn have been studied to understand the electronic charge distributions and its band gap (5.0514 eV/245.45 nm). Density of states (DOS), partial density of states (PDOS) and total density of states (TDOS) with respect to functional groups were computed to investigate the electron densities of functional groups in the molecule. Natural bond orbital (NBO) has been performed to explore the intramolecular π-π* interaction of the compound.

First Principles Study on Adsorption for Different Concentration of H2S on Fe(100)

2014 ◽  
Vol 1015 ◽  
pp. 521-525 ◽  
Author(s):  
Qiang Zhang ◽  
Ping Jun Hu ◽  
Qiang Luo ◽  
Yi Qiu ◽  
Zeng Ling Ran
Keyword(s):  
Density Of States ◽  
First Principles ◽  
Function Theory ◽  
Surface Adsorption ◽  
Density Function Theory ◽  
Partial Density ◽  
Total Density ◽  
Generalized Gradient ◽  
Generalized Gradient Approximation ◽  
Total Density Of States

Using the first principles method, which is based on the density function theory (DFT), the structures and electronic properties for different concentration of H2S are adsorbed on the Fe (100) surface, and their molecular orbital and absorption energies were calculated with the generalized gradient approximation. The results show that, whether one or two molecules of H2S adsorpted Fe (100) surface, adsorption of single molecules Fe (100) surface partial density of states between pure Fe (100) and two molecules, and the total density of states is mainly composed of 3d electronic contribution.

Elastic Properties and Electronic Structure of WS2 under Pressure from First-principles Calculations

2017 ◽  
Vol 72 (4) ◽  
pp. 295-301 ◽  
Author(s):  
Li Li ◽  
Zhao-Yi Zeng ◽  
Ting Liang ◽  
Mei Tang ◽  
Yan Cheng
Keyword(s):  
Density Of States ◽  
First Principles ◽  
External Pressure ◽  
Band Gaps ◽  
Partial Density ◽  
Total Density ◽  
Transition Metal Dichalcogenide ◽  
First Principles Calculations ◽  
First Time ◽  
Total Density Of States

AbstractThe influence of pressure on the elastic and mechanical properties of the hexagonal transition-metal dichalcogenide WS2 is investigated using the first-principles calculations. With the increase in pressure, the lattice parameters and the volume of WS2 decrease, which is exactly in agreement with the available experimental data and other calculated results. The elastic constants Cij, bulk modulus B, shear modulus G, Young’s modulus E, and Poisson’s ratio σ of WS2 also increase with pressure. At last, for the first time, the band gaps of energy, the partial density of states, and the total density of states under three different pressures are obtained and analysed. It is found that the band gap of WS2 decreases from 0.843 to 0 eV when the external pressure varies from 0 to 20 GPa, which implies that WS2 may transform from semiconductors to semimetal phase at a pressure about 20 GPa.

First-Principles Study on Ga-N Co-Doped P-Type ZnO

2011 ◽  
Vol 299-300 ◽  
pp. 498-502 ◽  
Author(s):  
Hong Sheng Zhao ◽  
Yu Dan Gu ◽  
Nan Zhang ◽  
Ya Hong Gao
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Donor Acceptor ◽  
P Type ◽  
Total Density Of States ◽  
Co Doped

Based on the density functional theory, the structure of pure ZnO, N doped, and Ga-N/Ga-2N co-doped wurtzite ZnO was calculated by using first-principle plane wave ultrasoft pseudopotential method. Electronic structures of these ZnO-based doping syetems were studied. The calculations of band structure, total density of states, and partial density of states show that Ga-2N donor/acceptor co-doped ZnO is easier to implement the p-type ZnO than other cases.

scholarly journals Experimental and computational study on roles of WOx promoting strong metal support promoter interaction in Pt catalysts during glycerol hydrogenolysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tinnakorn Saelee ◽  
Poonnapa Limsoonthakul ◽  
Phakaorn Aphichoksiri ◽  
Meena Rittiruam ◽  
Mongkol Lerdpongsiripaisarn ◽  
...  
Keyword(s):  
Density Of States ◽  
Design Guidelines ◽  
Total Density ◽  
High Electron ◽  
Metal Support Interaction ◽  
Metal Support ◽  
Glycerol Hydrogenolysis ◽  
The Stability ◽  
Total Density Of States ◽  
Promoter Interaction

AbstractBiodiesel is of high interest due to increased demand for energy with the concern regarding more sustainable production processes. However, an inevitable by-product is glycerol. Hence, the conversion of this by-product to higher-value chemicals, especially 1,3-propanediol (1,3-PDO) via glycerol hydrogenolysis reaction, is one of the most effective pathways towards a profitable process. In general, this process is catalyzed by a highly active Pt-based catalyst supported on γ-Al2O3. However, its low 1,3-PDO selectivity and stability due to surface deactivation of such catalysts remained. This led to the surface modification by WOx to improve both the selectivity by means of the increased Brønsted acidity and the stability in terms of Pt leaching-resistance. Hence, we applied experimental and density functional theory (DFT)-based techniques to study the fundamentals of how WOx modified the catalytic performance in the Pt/γ-Al2O3 catalyst and provided design guidelines. The effects of WOx promoter on improved activity were due to the shifting of the total density of states towards the antibonding region evident by the total density of states (TDOS) profile. On the improved 1,3-PDO selectivity, the main reason was the increasing number of Brønsted acid sites due to the added WOx promoter. Interestingly, the stability improvement was due to the strong metal-support interaction (SMSI) that occurred in the catalyst, like typical high leaching-resistant catalysts. Also, the observed strong metal-support-promoter interaction (SMSPI) is an additional effect preventing leaching. The SMSPI stemmed from additional bonding between the WOx species and the Pt active site, which significantly strengthened Pt adsorption to support and a high electron transfer from both Pt and Al2O3 to WOx promoter. This suggested that the promising promoter for our reaction performed in the liquid phase would improve the stability if SMSI occurred, where the special case of the WOx promoter would even highly improve the stability through SMSPI. Nevertheless, various promoters that can promote SMSPI need investigations.

scholarly journals THE PHONON SPECTRUM OF THE OCTAGONAL TILING

1993 ◽  
Vol 07 (06n07) ◽  
pp. 1505-1525 ◽  
Author(s):  
J. LOS ◽  
T. JANSSEN ◽  
F. GÄHLER
Keyword(s):  
Specific Heat ◽  
Density Of States ◽  
Phonon Spectrum ◽  
Low Frequency ◽  
Debye Model ◽  
Square Lattice ◽  
Total Density ◽  
Unit Cells ◽  
Linear Behaviour ◽  
Total Density Of States

A study of the phonon spectrum of the octagonal tiling is presented, by calculating and analysing the properties of the spectrum of perfect and randomized commensurate approximants with unit cells containing up to 8119 vertices. The total density of states, obtained by numerical integration over the Brillouin zone, exhibits much structure, and in the low frequency range of the spectrum there is deviation from the normal linear behaviour in the form of pseudogaps. For randomized approximants these pseudogaps disappear and the density of states is globally smoothened. It turns out that the widths of the gaps in the dispersion vanish in the low frequency limit. Therefore the scaling behaviour of the lowest branches tends to the behaviour of an absolutely continuous spectrum, which is not the case at higher frequencies. As an application, the vibrational specific heat of the different tiling models is calculated and compared to the specific heat of a square lattice and of a Debye model.

Electronic Properties of Calcium and Zirconium Co-Doped BaTiO3

2020 ◽  
Vol 1010 ◽  
pp. 308-313
Author(s):  
Akeem Adekunle Adewale ◽  
Abdullah Chik ◽  
Ruhiyuddin Mohd Zaki
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Density Of States ◽  
Energy Band ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Energy Band Gap ◽  
Wide Energy ◽  
Direct Band

Barium titanate (BaTiO3) is a perovskite based oxides with many potential application in electronic devices. From experimental report BaTiO3 has wide energy band gap of about 3.4 eV which by doped with Ca and Zr at A- and B- sites respectively can enhance their piezoelectric properties. Using first principles method within the density functional theory (DFT) as implement in Quantum Espresso (QE) with the plane wave pseudo potential function, the influence of the Ca and Zr doping in BaTiO3 are studied via electronic properties: band structure, total density of states (TDOS) and partial density of states (PDOS). The energy band gap calculated was underestimation which is similar to other DFT work. Two direct band gap where observed in Ba0.875Ca0.125Ti0.875Zr0.125O3 sample at Γ- Γ (2.31 eV) and X- X (2.35 eV) symmetry point.

First-Principles Study of Electronic Structure and Optical Properties of V-Doped CrSi2

2015 ◽  
Vol 1104 ◽  
pp. 125-130 ◽  
Author(s):  
Fang Gui ◽  
Shi Yun Zhou ◽  
Wan Jun Yan ◽  
Chun Hong Zhang ◽  
Shao Bo Chen
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Density Of States ◽  
Density Functional ◽  
Partial Density ◽  
Optical Parameters ◽  
Total Density ◽  
Type Semiconductor ◽  
Refractive Index Increase ◽  
P Type

The electronic structure and optical properties of V-doped CrSi2 have been calculated by using the first-principle peudo-potential plane-wave method based on the density functional theory.The parameters and properties of structure were given and the theory data were offered to research the effect of V doping into CrSi2. The calculations of energy band structure, total density of states, partial density of states of V-doped CrSi2were analysed. Fermi level enters into valence band which makes the V-doped CrSi2to be p-type semiconductor that improves the electrical conductivity of material. Additionally, the optical parameters of V-doped CrSi2were also discussed. It was found that both static dielectric constant and static refractive index increase after doping.

Transport properties of impurity-doped VO2

1976 ◽  
Vol 54 (4) ◽  
pp. 413-423 ◽  
Author(s):  
J. M. Reyes ◽  
M. Sayer ◽  
A. Mansingh ◽  
R. Chen
Keyword(s):  
Density Of States ◽  
Ac Conductivity ◽  
Energy Gap ◽  
Dc Conductivity ◽  
Total Conductivity ◽  
Total Density ◽  
Impurity Doped ◽  
Impurity Sites ◽  
Total Density Of States ◽  
Band Conduction

The temperature dependence of the DC conductivity in the semiconducting phase of undoped and Al, Cr, and Ti-doped VO2 has been interpreted with the aid of AC conductivity and thermopower measurements down to 77 K. A hopping conductivity is shown to be dominant for T < 180 K and to make up about 10% of the total conductivity at the metal–semiconductor transition temperature. The frequency dependence of the AC conductivity, σ~fs, is shown to be sensitive to crystalline disorder through the parameter s; s ~0.5 for 'good' crystals and 0.7–0.9 for highly doped or nonstoichiometric material. For the best crystals, a phonon drag contribution is found to exist in the thermopower. The hopping component of the DC conductivity is analyzed in terms of variable range hopping within a nonuniform density of states. For a total density of states between 1018–1020 this leads to a localization radius of 3–11 Å and the conclusion that the position of the Fermi level within the gap strongly influences the relative contributions of hopping and band conduction. A model for the density of states within the energy gap for both pure and doped VO2 is presented on the basis of localized correlations between electrons on pairs of vanadium or vanadium–impurity sites.

X-Ray Emission and Absorption Spectroscopy with Binary Amorphous Alloys from the B-Co-, B-Ni-, Co-P-, Co-Ti-, Cu-Mg-, Cu-Ti-, Mg-Zn-, Ni-P-, and Ni-Ti-Systems

1984 ◽  
Vol 39 (12) ◽  
pp. 1175-1183 ◽  
Author(s):  
S. Falch ◽  
P. Lamparter ◽  
S. Steeb
Keyword(s):  
Absorption Spectroscopy ◽  
Melt Spinning ◽  
Emission Spectra ◽  
Local Symmetry ◽  
Partial Density ◽  
Energy Curve ◽  
Electronic Charge ◽  
X Ray Diffraction ◽  
X Ray ◽  
Amorphous Phases

X-ray emission and absorption spectroscopy has been used to determine the partial density of occupied and unoccupied states in various metallic glasses. The X-ray emission spectra also indicate a possible electronic charge transfer between the alloyed atoms. The experiments were done by means of an electron microprobe. Amorphous Mg2Cu was prepared by ionic sputtering, the glasses of the Mg-Cu-, Mg-Zn-, Cu-Ti-, Co-Ti-, Co-B-, Co-P-, Ni-Ti-, Ni-B-, and Ni-Psystems by the melt-spinning method. From the measurements it is concluded that the amorphous phase is stabilized by compound formation. A combination with results of X-ray diffraction measurements on amorphous Mg2Cu indicates that the glassy structures should be favoured by a correlation between the atoms of higher electronegativity. The shape of the density of unoccupied states vs. energy curve shows that the local symmetry around the Zn- and Cu-atoms in the amorphous phases differs from that in the corresponding crystalline phases. For the transition-metalloid glasses evidence for a fcc-like local short range order is found.

Physical properties of ThCr2Si2-type Rh-based compounds ARh2Ge2(A = Ca, Sr, Y and Ba): DFT based first-principles investigation

2018 ◽  
Vol 32 (32) ◽  
pp. 1850357 ◽  
Author(s):  
M. U. Salma ◽  
Md. Atikur Rahman
Keyword(s):  
Thermal Conductivity ◽  
Density Of States ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Coating Materials ◽  
Metallic Behavior ◽  
Density Maps ◽  
Debye Temperatures ◽  
Low Energies

In this paper, we have explored the physical, mechanical, chemical bonding, dialectical and thermodynamic properties of ARh2Ge2 (A = Ca, Sr, Y and Ba) theoretically for the first time. This investigation has been completed by density functional theory (DFT) calculations with the help of CASTEP code. The structural optimized factors of ARh2Ge2 (A = Ca, Sr, Y and Ba) are in excellent concurrence with the existing experimental data. The observed elastic constants are positive and prove the mechanical constancy for all these compounds. The calculated Pugh’s ratio and Poisson’s ratio show the ductile behaviors of Ca/YRh2Ge2 and brittleness behaviors of Sr/BaRh2Ge2, whereas the Cauchy pressure indicates the ductility for all these phases. The anisotropic factors, universal anisotropy indicator and fraction of anisotropy in compression and shear ensure the elastically anisotropic nature for all these phases. Bulk modulus and hardness values indicate that Sr/BaRh2Ge2 are soft and easily machinable in comparison with Y/CaRh2Ge2. The analysis of the band structure diagrams as well as density of states (total density of states and partial density of states) evidence the metallic behavior for all the compounds. The analysis of Mulliken bond populations and charge density maps give the existence of covalent and metallic bonding in these compounds. The optical properties point out that all phases can be used as coating materials at low energies. For all the phases the Debye temperatures have been calculated via elastic constant data. We have also evaluated the minimum thermal conductivity for these compounds. All compounds possess the relatively low minimum thermal conductivity with the low value of Debye temperatures which also evidence that all compounds could be applied like thermal fence covering material.

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