scholarly journals Hydrolysis Mechanism of Bismuth in Chlorine Salt System Calculated by Density Functional Method

2020 ◽  
Vol 71 (6) ◽  
pp. 178-193
Author(s):  
Liao Chunfa ◽  
Xu Zhenxin ◽  
Zou Jianbai ◽  
Jiang Pinguoo
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Energy Gap ◽  
Density Functional Method ◽  
Covalent Bond ◽  
Salt System ◽  
Hydroxyl Group ◽  
Partial Density ◽  
Hydroxyl Groups ◽  
Total Density

Based on the density functional theory, this paper presents the calculated cellular electronic properties of BiCl3, BiOCl and Bi3O4Cl, including unit cell energy, band structure, total density of states, partial density of states, Mulliken population, overlapping population, etc. Combined with the thermodynamic analysis of Bi3+ hydrolysis process in chlorine salt system, the conversion mechanism of oxychloride bond in BiCl3 to form BiOCl and Bi3O4Cl by hydrolysis, ethanololysis and ethylene glycol alcohololysis was obtained by infrared spectroscopy. The results indicate that the energy of Bi3O4Cl cell system was lower than that of BiOCl cell, indicating that the structure of Bi3O4Cl was more stable. From the analysis of bond fluctuation, the electron nonlocality in BiOCl belt was relatively large, and the orbital expansibility was strong; thus the structure of BiOCl was relatively active. The state density map of Bi3O4Cl had the widest energy gap, i.e., the covalent bond between Bi3O4Cl was stronger than BiOCl. Therefore, the hydrolysis of BiCl3 would preferentially generate Bi3O4Cl with a more stable structure. The number of charge arrangement, overlapping population and infrared spectrogram indicate that there were two basic ways in the hydrolysis and alcoholysis of BiCl3. Firstly, two chlorine atoms in BiCl3 were replaced by hydroxyl groups ionized by water and alcohol to form [Bi(OH)2Cl] monomer, and BiOCl and Bi3O4Cl were formed by intra-molecular dehydration or inter-molecular dehydration. The other way was that the Bi atom directly reacted with the OH ionized by water and alcohol to form the [Bi-OH] monomer, and the Cl atom replaced the H atom on the hydroxyl group in the [Bi-OH] monomer to further form BiOCl and Bi3O4Cl.

First-principles calculations of electronic structures and ferromagnetism of Fe3Si(001)//MgO(001) films

2018 ◽  
Vol 32 (24) ◽  
pp. 1850272
Author(s):  
Jing Xie ◽  
Quan Xie
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Energy Gap ◽  
Covalent Bond ◽  
Total Density ◽  
First Principles Calculations ◽  
Si Films

The first-principles calculations based on density functional theory (DFT) were carried out in investigating electronic structures and ferromagnetism of Fe3Si films epitaxial on MgO(001). Firstly, the various geometric structures of Fe3Si(001)//MgO(001) constructed near lattice constant c = 3.995 Å were optimized to gain the most steady equilibrium state at c = 3.980 Å. Then, the calculated cohesive energy and negative heat of formation indicate that Fe3Si(001)//MgO(001) formed in this manner obtain high structural stability. The calculated results of spin-polarized energy band structures and density of states show that Fe3Si(001)//MgO(001) exhibit the metallic feature whose bonding orbitals are constituted by covalent bond and metallic bond. Two peaks located in both the sides of the Fermi level and the total density of states (TDOS) in this energy range are all due to the Fe 3d states, which implies that the pseudo energy gap exists in the Fermi level and covalent electron orbit hybridization takes place. Ferromagnetism of Fe3Si(001)//MgO(001) are determined by the 3d states of Fe atoms. There are two occupied sites for Fe atoms with different local magnetic moments, which is 1.34 [Formula: see text]/atom for Fe[A, C] atoms and a value of 2.68 [Formula: see text]/atom for Fe[B] atoms, likewise indicating Fe3Si films epitaxial on MgO(001) are ferromagnetic.

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.

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.

scholarly journals Study on Electronic and Optical Properties of Graphene Oxide Under an External Electric Field From First-principles

2021 ◽  
Author(s):  
Abdehafid Najim ◽  
Omar BAJJOU ◽  
Mustapha BOULGHALLAT ◽  
Mohammed Khenfouch ◽  
Khalid Rahmani
Keyword(s):  
Optical Properties ◽  
Graphene Oxide ◽  
Electric Field ◽  
Band Gap ◽  
External Electric Field ◽  
Density Of States ◽  
Density Functional ◽  
Partial Density ◽  
Total Density ◽  
Electronic And Optical Properties

Abstract Electronic and optical properties of graphene oxide (GO), under an external electric field (Eext) applied in three directions of space (x, y, z), are investigated using the density functional theory (DFT). The application of the Eext, causes a significant modifications to the electronic and optical properties of GO material. It has change the band gap, total density of states (TDOS), partial density of states (PDOS), absorption coefficient (α), dielectric function, optical conductivity, refractive index and loss function. The band gap of GO layer increases under the effects of the Eext, applied in x and y directions. On the other hand, for z direction, the band gap decreases by the effects of the Eext. The peaks of the TDOS around the Fermi level, change by the Eext applied in (x, y, z) directions. The α peaks of the GO sheet, decreases by the Eext applied in x direction, and increases if Eext applied in y and z directions. It is found that, the electronic and optical properties of GO layer, could be affected by the effects of the Eext and by its direction of application.

scholarly journals Электронные состояния наноструктурированных систем: титан и диоксид циркония

2018 ◽  
Vol 60 (10) ◽  
pp. 1861
Author(s):  
В.Г. Заводинский
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Energy Gap ◽  
Density Functional Method ◽  
Three Dimensional ◽  
Electronic States ◽  
Functional Method ◽  
Density Of Electronic States ◽  
Nanostructured Systems ◽  
Ionic Bonds

AbstractThe density functional method with pseudopotentials are used to study the electron states of nanoparticles and nanostructured systems: chains, films, and three-dimensional nanosystems of titanium and zirconia. It is shown that all studied titanium nanosystems have the density of electronic states (DES) of the metallic type, but zirconia nanosystem demonstrates a dielectric energy gap in the vicinity of the Fermi level. The density of states of nanostructured titanium is close in shape to DES of the single crystal but has a smoother shape due to disordering of the atomic arrangement. The forbidden band width of the nanostructured zirconia is smaller as compared to the corresponding width in crystalline ZrO_2, supposedly because of incomplete saturation of ionic bonds.

scholarly journals Ultra-wide bandgap semiconductor behavior of NaCaF3 fluoro-perovskite with external static isotropic pressure and its impact on optical properties: First-principles computation

2021 ◽  
Author(s):  
Syed Sajid Ali Gillani ◽  
Nisar Fatima ◽  
M. Shakil ◽  
R. Kiran ◽  
M. B. Tahir ◽  
...  
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Band Gap ◽  
Density Of States ◽  
Density Functional ◽  
External Pressure ◽  
Partial Density ◽  
Total Density ◽  
Isotropic Pressure ◽  
The Impact

Abstract A comprehensive theoretical study to investigate the outcomes of externally applied static isotropic pressure (0 GPa - 50 GPa) on electronic, optical and structural properties of NaCaF3, using density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with ultra-soft pseudo-potential USP plane wave and Perdew Burke Ernzerhof (PBE) exchange-correlation functional of Generalized Gradient Approximation (GGA), is reported. The electronic bandgap shows the increasing trend 4.773 eV - 6.203 eV (direct bandgap) with increasing external pressure. The increase in bandgap is significant up to 20 GPa as compared to higher external pressures. The mystery of increasing band gap is nicely decoded by total density of states (TDOS) and elemental partial density of states (EPDOS). Optical properties have been calculated to analyze the impact of increment in band gap on them. We observed that highest peak of energy loss function L(w) shows the blue shift which confirms the increment of band gap. At zero photon energy, for 0 GPa, the static refractive index n(w) has value of 1.4456. After applying external pressure, there is a slight increase in n(w) which favors the semiconducting behavior of ternary compound. The energy points at which the absorption peak is maxima, the refractive index has lowest value.

scholarly journals Molecular Modeling of Ammonia Gas Adsorption onto the Kaolinite Surface with DFT Study

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 46 ◽  
Author(s):  
Qi Cheng ◽  
Yongbing Li ◽  
Xiaojuan Qiao ◽  
Yang Guo ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Density Functional ◽  
Gas Adsorption ◽  
Hydroxyl Group ◽  
Partial Density ◽  
Hydroxyl Groups ◽  
High Porosity ◽  
Ammonia Gas ◽  
Nh3 Adsorption ◽  
Kaolinite Surface

With high porosity and being one of the most abundant clay minerals, dried kaolinite may be an excellent adsorbent to remove ammonia gas (NH3). Here, the plane wave pseudopotential method based on density functional theory (DFT) was used to explore the mechanism of ammonia gas adsorption on the dried kaolinite, the Mulliken electric charge, and the partial density of states of atoms of the NH3/kaolinite (001) system. NH3 adsorption on kaolinite can happen in three different type adsorption positions: “top”, “bridge” and “hollow”. The “hollow” position is enclosed by two "upright" hydroxyl groups perpendicular to the (001) surface of kaolinite and a "lying" hydroxyl group parallel to the surface. At this position, the adsorption is the most stable and has the highest adsorption energy. The nitrogen atom of the NH3 molecule bonds with the hydrogen atom in the "upright" hydroxyl group on the (001) surface and its hydrogen atom forms HN…O hydrogen bond with oxygen atom in the "lying" hydroxyl group, which leads to the NH3 stably adsorbed on kaolinite (001) surface. A small part of electrons transfer between NH3 molecules and kaolinite creates weakly electrostatic adsorption between them.

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.

First-principles study on the structural, elastic and electronic properties of Ti4N3 and Ti6N5 under high pressure

2017 ◽  
Vol 31 (36) ◽  
pp. 1750349 ◽  
Author(s):  
Ruike Yang ◽  
Bao Chai ◽  
Chuanshuai Zhu ◽  
Qun Wei ◽  
Zheng Du
Keyword(s):  
Electronic Properties ◽  
Young’S Modulus ◽  
Density Of States ◽  
First Principles ◽  
Density Functional ◽  
Young's Modulus ◽  
Ambient Pressure ◽  
Pressure Rise ◽  
Partial Density ◽  
Total Density

The structural, elastic and electronic properties of Ti4N3 and Ti6N5 have been systematically studied by first-principles calculations based on density functional theory (DFT) with generalized gradient approximation (GGA) and local density approximation (LDA). Basic physical properties for Ti4N3 and Ti6N5, such as the lattice constants, the bulk modulus, shear modulus, and elastic constants are calculated. The results show that Ti4N3 and Ti6N5 are mechanically stable under ambient pressure. The phonon dispersion spectra are researched throughout the Brillouin zone via the linear response approach as implemented in the CASTEP code, which indicate the optimized structures are stable dynamically. The Young’s modulus E and Poisson’s ratios [Formula: see text] are also determined within the framework of the Voigt–Reuss–Hill approximation. The analyses show that Ti4N3 is more ductile than Ti6N5 at the same pressure and ductility increases as the pressure increases. Moreover, the anisotropies of the Ti4N3 and Ti6N5 are discussed by the Young’s modulus at different directions, and the results indicate that the anisotropy of the two Ti–N compounds is obvious. The total density of states (TDOS) and partial density of states (PDOS) show that the TDOS of TiN, Ti4N3 and Ti6N5 originate mainly from Ti “d” and N “p” states. The results show that Ti4N3 and Ti6N5 present semimetal character. Pressure makes the level range of DOS significantly extended, for TiN, Ti4N3 and Ti6N5. The TDOS decreases with the pressure rise, at Fermi level.

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