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 Электронная структура, оптические свойства и поведение под давлением в соединениях CdB-=SUB=-4-=/SUB=-O-=SUB=-7-=/SUB=- и HgB-=SUB=-4-=/SUB=-O-=SUB=-7-=/SUB=-

2018 ◽  
Vol 60 (9) ◽  
pp. 1662
Author(s):  
А.С. Шинкоренко ◽  
В.И. Зиненко ◽  
М.С. Павловский
Keyword(s):  
Phase Transition ◽  
Density Functional Theory ◽  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
Functional Theory ◽  
Structural Modifications ◽  
The Density Functional Theory

AbstractAb initio calculations of the structural, electronic, and optical properties of the CdB_4O_7 and HgB_4O_7 tetraborate compounds in three structural modifications with the Pbca , Cmcm , and Pmn 2_1 symmetry have been performed in the framework of the density functional theory using the VASP package. The calculations of the electronic band structure showed that these compounds in all the investigated modifications are dielectrics with a band gap of 2–4 eV. The calculation of the structural properties of the tetraborates under pressure showed that the phase transition between the Pbca and Pmn 2_1 structures in cadmium and mercury tetraborates occurs under pressures of 4.8 and 4.7 GPa, respectively.

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.

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.

FIRST-PRINCIPLES STUDIES ON THE ELECTRONIC STRUCTURE OF LuPd2Si2

2009 ◽  
Vol 23 (32) ◽  
pp. 5929-5934 ◽  
Author(s):  
T. JEONG
Keyword(s):  
Band Structure ◽  
First Principles ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Spin Orbit Coupling ◽  
Electronic Band ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structure Scheme

The electronic band structure of LuPd 2 Si 2 was studied based on the density functional theory within local density approximation and fully relativistic schemes. The Lu 4f states are completely filled and have flat bands around -5.0 eV. The fully relativistic band structure scheme shows that spin–orbit coupling splits the 4f states into two manifolds, the 4f7/2 and the 4f5/2 multiplet.

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.

Pressure Effect on the Electronic Properties of Cerium Monochalcogenides CeX (X=S, Se, Te) Using Modified Becke-Johnson Exchange Potential and LDA+U

2014 ◽  
Vol 925 ◽  
pp. 390-395
Author(s):  
Noureddine Amrane ◽  
Maamar Benkraouda
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Exchange Potential ◽  
Full Potential ◽  
Electronic Band ◽  
Functional Theory ◽  
Augmented Plane Wave ◽  
The Density Functional Theory ◽  
Linearized Augmented Plane Wave

We present a systematic and comparative study of the electronic properties of CeX monochalcogenides, The density of state (DOS) and electronic band structure of CeX (X=S, Se, Te) have been calculated using the full-potential linearized augmented plane-wave (FP-LAPW) + local orbital (lo) method based on the density functional theory (DFT), which is implemented in WIEN2k code. The trends in the high pressure behavior of these systems are discussed. Four approximations for the exchange-correlation functional have been used, the GGA's of Perdew-Burke-Ernzherhof. (PBE08) , Engel-Vosko (EV93), a modified version of the exchange potential proposed by Becke and Johnson (MBJ), and LDA+U is used to calculate the band gaps at different pressures. All methods allow for a description of the Ce f electrons as either localized or delocalized, it is found that the underestimations of the bandgap by means of LDA-GGA and Engel-Vosko are considerably improved by using the modified Becke-Johnson (MBJ) potential for all compounds in the series, On the other hand, LDA+U, method gives good results for the lighter chalcogenides, but it fails to give good results for the heavier cerium monochalcogenides.

Ab initioMolecular and Solid State Studies of the FeII Spin Cross-over System [Fe(btz)2(NCS)2] (btz = 2.2’-bis-4.5-dihydrothiazine)

2008 ◽  
Vol 63 (2) ◽  
pp. 154-160 ◽  
Author(s):  
Lara Kabalan ◽  
Samir F. Matar ◽  
Mirvat Zakhour ◽  
Jean François Létarda
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Crystalline Solid ◽  
Infrared And Raman Spectra ◽  
Full Account ◽  
Electronic Band ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structure Properties

Ab initio computations within the density functional theory are reported for the spin cross-over complex [Fe(btz)2(NCS)2] (btz = 2.2'-bis-4.5-dihydrothiazine), where 3d6 FeII is characterized by high-spin (HS t2g4, eg2) and low-spin (LS t2g6, eg0) states. Results of infrared and Raman spectra for the isolated molecule are complemented for the crystalline solid with a full account of the electronic band structure properties: the density of states assessing the crystal field effects and the chemical bonding, assigning a specific role to the Fe-N interactions within the coordination sphere of FeII

First-Principle Study of Electronic Structures of Y-Doped Mg2Si

2011 ◽  
Vol 689 ◽  
pp. 102-107 ◽  
Author(s):  
Wen Hao Fan ◽  
Rui Xue Chen ◽  
Pei De Han ◽  
Qing Sen Meng
Keyword(s):  
Electronic Structure ◽  
Electronic Structures ◽  
Density Functional ◽  
Energy Structure ◽  
First Principle ◽  
Functional Theory ◽  
Structure Relaxation ◽  
Substitution Site ◽  
The Density Functional Theory ◽  
Correlation Potential

The formation energy, structure relaxation and electronic structure of Mg2Si and Y-doped Mg2Si are investigated using first-principle calculations based the density functional theory. The general gradient approximation was used to treat the exchange and correlation potential. The calculated electronic structure shows that Mg2Si is a semiconductor with a direct gap of 0.27eV at G point. The preferential substitution site of Y inside Mg2Si is determined to be Mg. Y-doping makes the Si atoms around the impurity outward relaxation and increases the Seebeck coefficient, electrical conductivity and thermal conductivity of Mg2Si crystals simultaneously.

Microcrystalline β-RbNd(MoO4)2: spin polarizing DFT+U

RSC Advances ◽  
2015 ◽  
Vol 5 (56) ◽  
pp. 44960-44968 ◽  
Author(s):  
A. H. Reshak
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Electronic Charge ◽  
Charge Density Distribution ◽  
Electronic Charge Density ◽  
Electronic Band ◽  
Functional Theory ◽  
Hubbard Hamiltonian ◽  
The Density Functional Theory ◽  
Structure Density

Using the density functional theory plus Hubbard Hamiltonian we have investigated the spin up/down electronic band structure, density of states, electronic charge density distribution and the dispersion of the optical properties of microcrystalline β-RbNd(MoO4)2.

scholarly journals Влияние размерных эффектов на электронную структуру гексагонального теллурида галлия

2018 ◽  
Vol 60 (9) ◽  
pp. 1645
Author(s):  
А.В. Кособуцкий ◽  
С.Ю. Саркисов
Keyword(s):  
Density Functional ◽  
Electronic Band Structure ◽  
Bulk Material ◽  
Structural Parameters ◽  
Van Der Waals Interactions ◽  
Electronic Band ◽  
Functional Theory ◽  
Lower Conduction Band ◽  
The Density Functional Theory ◽  
Indirect Band Gap

AbstractUsing methods of the density functional theory, the electronic band structure of a hexagonal modification of the layered GaTe semiconductor has been calculated. The structural parameters of a bulk crystal with the β-polytype symmetry have been determined taking into account van der Waals interactions and agree with experimental data for polycrystalline films within 2%. Estimates for the position of extrema of the upper valence band and the lower conduction band have been obtained with respect to the vacuum level for bulk β-GaTe and for ultrathin plates with the number of elementary layers ranging from 1 to 10, which corresponds to a thickness range of 0.5–8 nm. The calculations demonstrate that hexagonal GaTe is an indirect band gap semiconductor with a forbidden band width varying from 0.8 eV in the bulk material to 2.3 eV in the monolayer.

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