scholarly journals Атомная структура и энергия когезии кластеров ZnSe и CdSe

2019 ◽  
Vol 61 (4) ◽  
pp. 786
Author(s):  
Л.И. Овсянникова
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Energy Gap ◽  
First Principle ◽  
External Layer ◽  
Functional Theory ◽  
First Principle Calculations ◽  
The Stability ◽  
First Time ◽  
Gap Width

AbstractThe first-principle calculations of the atomic and electronic structures of fullerene-like Zn_ n Se_ n and Cd_ n Se_ n have been carried out for n = 12, 36, 48, and 60. A model of two-layer fullerene-like (ZnSe)_60 and (CdSe)_60 clusters with mixed sp ^2/ sp ^3 bonds has been built for the first time. Ab initio calculations are performed in terms of the electron density functional and the hybrid B3LYP functional theory. The stability and the energy gap width of the clusters are estimated in the dependence on the number of atoms in a cluster and its geometry. It is shown that the relaxation of 1.7–1.8-nm two-layer (ZnSe)_60 and (CdSe)_60 clusters with mixed sp ^2/ sp ^3 bonds is accompanied by splitting out of the external layer.

scholarly journals Атомная структура и энергия когезии изолированных кластеров SiC

2020 ◽  
Vol 62 (6) ◽  
pp. 974
Author(s):  
Л.И. Овсянникова
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Energy Gap ◽  
Cohesion Energy ◽  
First Principle ◽  
Sphalerite Structure ◽  
Functional Theory ◽  
The Stability ◽  
First Time ◽  
Gap Width

The first-principle calculations of the atomic and electronic structures and cohesion energy of fullerene-like Si60C60 clusters have been carried out. A model of two-layer fullerene-like Si12C12@Si48C48 cluster with mixed sp2/sp3 bonds has been built for the first time. Ab initio calculations are performed in terms of the electron density functional and the hybrid B3LYP functional theory. The stability and the energy gap width of the clusters are estimated in the dependence on its geometry. It is shown that cohesion energy of two-layer fullerene-like Si12C12@Si48C48 cluster exceeds the cohesion energy of the other fullerene-like clusters with the same number of atoms, but is inferior to the SiC cluster with sphalerite structure. The relaxation of two-layer cluster is shift on outward the surface layer occurs.

Electronic Structures of Vacancy Defective Chiral (6,2) SiC Nanotubes

2017 ◽  
Vol 896 ◽  
pp. 3-8
Author(s):  
Ke Jian Li ◽  
Hong Xia Liu
Keyword(s):  
Density Functional Theory ◽  
Silicon Carbide ◽  
Electronic Structures ◽  
Density Functional ◽  
First Principle ◽  
Defect Level ◽  
Functional Theory ◽  
Vacancy Defects ◽  
First Principle Calculations ◽  
Silicon Carbide Nanotubes

Vacancy defects are common defects formed in the syntheses of silicon carbide nanotubes (SiCNTs) and seriously impact the electronic structures of the nanotubes. With first-principle calculations based on density functional theory (DFT), vacancy defective (6,2) SiCNTs are studied. Vacancies form a pair of fivefold and ninefold rings. Carbon vacancy introduces an occupied defect level near the top of the valence band and an unoccupied level in the conduction band. Three defect levels are found in the band gap of the SiCNT with a silicon vacancy. These results are helpful for investigations on SiCNT devices and sensors.

scholarly journals Elastic and optical properties of sillenites: First principle calculations

2020 ◽  
Vol 557 (1) ◽  
pp. 98-104 ◽  
Author(s):  
Husnu Koc ◽  
Selami Palaz ◽  
Sevket Simsek ◽  
Amirullah M. Mamedov ◽  
Ekmel Ozbay
Keyword(s):  
Optical Properties ◽  
Electronic Structures ◽  
Density Functional ◽  
Electronic Band Structure ◽  
First Principle ◽  
Electronic Band ◽  
Functional Theory ◽  
First Principle Calculations ◽  
Optical Functions ◽  
The Density Functional Theory

In the present paper, we have investigated the electronic structure of some sillenites - Bi12MO20 (M = Ti, Ge, and Si) compounds based on the density functional theory. The mechanical and optical properties of Bi12MO20 have also been computed. The second-order elastic constants have been calculated, and the other related quantities have also been estimated in the present work. The band gap trend in Bi12MO20 can be understood from the nature of their electronic structures. The obtained electronic band structure for all Bi12MO20 compounds is semiconductor in nature. Similar to other oxides, there is a pronounced hybridization of electronic states between M-site cations and anions in Bi12MO20. Based on the obtained electronic structures, we further calculate the frequency-dependent dielectric function and other optical functions.

scholarly journals First Principle Calculations for Silver Halides AgBr, AgCl, and AgF

2021 ◽  
Vol 9 (2) ◽  
pp. 71-75
Author(s):  
Akram H. Taha
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Total Density ◽  
First Principle ◽  
Silver Halides ◽  
Functional Theory ◽  
First Principle Calculations ◽  
Almost All ◽  
Total Density Of States ◽  
Good Agreement

Density functional theory (DFT) coupled with ) method are carried out to calculate the electronic structures of AgX (X; Br, Cl, and F). The effect of hybridizing between 4d orbital of Ag element and the p orbitals of the X in the valence band plays a very important role in the total density of states configuration. The electronic structure has been studied and all results were compared with the experimental and theoretical values. The importance of this work is that there is insufficient studies of silver halides corresponding the great importance of these compounds. Almost all the results were consistent with the previous studies mentioned here. We found the band gap of AgX to be 2.343 eV, 2.553 eV, and 1.677 eV for AgBr, AgCl, and AgF respectively which are in good agreement with the experimental results.      

scholarly journals The electronic structure of quasi-free-standing germanene on monolayer MX (M = Ga, In; X = S, Se, Te)

2015 ◽  
Vol 17 (29) ◽  
pp. 19039-19044 ◽  
Author(s):  
Zeyuan Ni ◽  
Emi Minamitani ◽  
Yasunobu Ando ◽  
Satoshi Watanabe
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Ab Initio ◽  
Electronic Structures ◽  
Density Functional ◽  
Free Standing ◽  
Functional Theory ◽  
The Stability ◽  
First Time

For the first time by using the ab initio density functional theory, the stability and electronic structures of germanene on monolayer GaS, GaSe, GaTe and InSe have been investigated.

Atomic and Electronic Structures of Au/TiO2 Catalyst – First-Principle Calculations –

2002 ◽  
Vol 738 ◽  
Author(s):  
Kazuyuki Okazaki ◽  
Yoshitada Morikawa ◽  
Shingo Tanaka ◽  
Satoshi Ichikawa ◽  
Koji Tanaka ◽  
...  
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Titanium Atom ◽  
First Principle ◽  
Hollow Site ◽  
Functional Theory ◽  
Surface Conditions ◽  
First Principle Calculations ◽  
The Density Functional Theory ◽  
Oxygen Atoms

ABSTRACTThe atomic and electronic structures of Au/TiO2(110) systems have been theoretically investigated based on the density functional theory. We have examined Au adsorption on the stoichiometric TiO2(110) surface and on the Ti-rich surface formed by the removal of bridging-oxygen atoms (VOB surface) and the O-rich surface formed by the removal of 6-fold titanium and bridging-oxygen atoms (VTi6OB surface). For the stoichiometric surface, the stable site for the Au adatom is the hollow site of one bridging-oxygen and two in-plane oxygen atoms or the on-top site above 5-fold titanium atom. For the Ti-rich VOB surface, the bridging site of 6-fold titanium atoms along [001] direction is the most stable. In addition, the vacant site of 6-fold titanium atom is the most stable for the O-rich VTi6OB surface. The adhesive energies between the Au adlayer and the TiO2 surface are larger for the non-stoichiometric surfaces than that for the stoichiometric surface. The charge transfer between the Au adatom and the substrate is small for stoichiometric surface. For the Ti-rich VOB surface, the electron transfer occurs from the 6-fold Ti to the Au, while from the Au to the in-plane oxygen for the O-rich VTi6OB surface. It can be said that the TiO2 surface conditions such as defects or non-stoichiometry strongly affect the adsorption energy and electron structure of the Au adsorbed system. This point should be closely related the catalytic property of the Au/TiO2 system.

The tuning effect of the electric field on the physical properties of some typical wurtzite semiconductors

2017 ◽  
Vol 31 (33) ◽  
pp. 1750310 ◽  
Author(s):  
Jia-Ning Li ◽  
San-Lue Hu ◽  
Hao-Yu Dong ◽  
Xiao-Ying Xu ◽  
Jia-Fu Wang ◽  
...  
Keyword(s):  
Electric Field ◽  
Physical Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Great Influence ◽  
Semiconductor Materials ◽  
Functional Theory ◽  
The Stability ◽  
Wurtzite Semiconductors

Under the tuning of an external electric field, the variation of the geometric structures and the band gaps of the wurtzite semiconductors ZnS, ZnO, BeO, AlN, SiC and GaN have been investigated by the first-principles method based on density functional theory. The stability, density of states, band structures and the charge distribution have been analyzed under the electric field along (001) and (00[Formula: see text]) directions. Furthermore, the corresponding results have been compared without the electric field. According to our calculation, we find that the magnitude and the direction of the electric field have a great influence on the electronic structures of the wurtzite materials we mentioned above, which induce a phase transition from semiconductor to metal under a certain electric field. Therefore, we can regulate their physical properties of this type of semiconductor materials by tuning the magnitude and the direction of the electric field.

scholarly journals Electronic Structure and Optical Properties of Co and Fe Doped ZnO

2016 ◽  
Vol 43 ◽  
pp. 23-28 ◽  
Author(s):  
Chun Ping Li ◽  
Ge Gao ◽  
Xin Chen
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Electronic Structures ◽  
Density Functional ◽  
Band Gaps ◽  
First Principle ◽  
Functional Theory ◽  
Doped Zno ◽  
Pseudo Potential ◽  
Co Doped

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.

Can boron form coordination complexes with diffuse electrons? Evidence for linked solvated electron precursors

2022 ◽  
Author(s):  
Zachary Jordan ◽  
Shahriar N. Khan ◽  
Benjamin A. Jackson ◽  
Evangelos Miliordos
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Molecular System ◽  
Hydrocarbon Chain ◽  
Solvated Electron ◽  
Excitation Energies ◽  
Functional Theory ◽  
Boron Complexes ◽  
The Stability ◽  
First Time

Abstract Density functional theory and ab initio multi-reference calculations are performed to examine the stability and electronic structure of boron complexes that host diffuse electrons in their periphery. Such complexes (solvated electron precursors or SEPs) have been experimentally identified and studied theoretically for several s- and d-block metals. For the first time, we demonstrate that a p-block metalloid element can form a stable SEP when appropriate ligands are chosen. We show that three ammonia and one methyl ligands can displace two of the three boron valence electrons to a peripheral 1s-type orbital. The shell model for these outer electrons is identical to previous SEP systems (1s, 1p, 1d, 2s). Further, we preformed the first examination of a molecular system consisting of two SEPs bridged by a hydrocarbon chain. The electronic structure of these dimers is very similar to that of traditional diatomic molecules forming bonding and anti-bonding σ and π orbitals. Their ground state electronic structure resembles that of two He atoms, and our results indicate that the excitation energies are nearly independent of the chain length for four carbon atoms or longer. These findings pave the way for the development of novel materials similar to expanded metals and electrides.

scholarly journals Development of a CALPHAD Thermodynamic Database for Pu-U-Fe-Ga Alloys

2019 ◽  
Vol 9 (23) ◽  
pp. 5040 ◽  
Author(s):  
Emily E. Moore ◽  
Patrice E.A. Turchi ◽  
Alexander Landa ◽  
Per Söderlind ◽  
Benoit Oudot ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Density Functional ◽  
Ternary Phase Diagram ◽  
Thermodynamic Database ◽  
Impurity Effects ◽  
Functional Theory ◽  
Formation Enthalpies ◽  
Temperature Ranges ◽  
The Stability ◽  
First Time

The interaction of actinides and actinide alloys such as the δ-stabilized Pu-Ga alloy with iron is of interest to understand the impurity effects on phase stability. A newly developed and self-consistent CALPHAD thermodynamic database is presented which covers the elements: Pu, U, Fe, Ga across their whole composition and temperature ranges. The phase diagram and thermodynamic properties of plutonium-iron (Pu-Fe) and uranium-iron (U-Fe) systems are successfully reassessed, with emphasis on the actinide rich side. Density functional theory (DFT) calculations are performed to validate the stability of the stoichiometric (Pu,U)6Fe and (Pu,U)Fe2 compounds by computing their formation enthalpies. These data are combined to construct the Pu-U-Fe ternary phase diagram. The thermodynamic assessment of Fe-Ga is presented for the first time and application to the quaternary Pu-U-Fe-Ga system is discussed.

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