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 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.

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.

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.

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.      

First-Principle Study of Structural and Electronic Properties of Ti-Doped SnO2

2013 ◽  
Vol 634-638 ◽  
pp. 2545-2549 ◽  
Author(s):  
Jing Kai Yang ◽  
Hong Li Zhao ◽  
Yan Zhu ◽  
Li Ping Zhao ◽  
Jian Li
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
First Principle ◽  
Generalized Gradient ◽  
Functional Theory ◽  
First Principle Calculations ◽  
Generalized Gradient Approximation ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Calculation Results

The structural and electronic properties of Ti-doped SnO2with 6.25 at.% are investigated with the first principle calculations based on the density functional theory within the generalized gradient approximation. The calculation results indicate that the crystal structure of Sn0.9375Ti0.0625O2possesses a smaller volume; the bond length of Ti-O is shorter than that of Sn-O; the relative angle θ change value of Sn-O-Sn→Ti-O-Ti is about 1.07%. Ti-O bond possesses more covalent ingredient and stronger bond energy than Sn-O bond. After the replacement of one Ti atom, O atom bonded with Ti atom possessed fewer electrons, the ratio of charges possessed by Ti atom and O atom dose not agree with the stoichiometry of compound, create more holes at the top of VB of Sn0.9375Ti0.0625O2, and lead to the increase of the conductivity.

scholarly journals AB INITIO CALCULATIONS OF THE CRYSTALLINE AND ELECTRONIC STRUCTURE OF 5-7 FLUOROGRAPHENE VARIETIES

2020 ◽  
pp. 326-337
Author(s):  
Максим Евгеньевич Беленков ◽  
Владимир Михайлович Чернов
Keyword(s):  
Density Functional ◽  
Density Functional Theory Method ◽  
Band Gaps ◽  
First Principle ◽  
Functional Theory ◽  
Graphene Layers ◽  
First Principle Calculations ◽  
Deformation Parameters ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties

Первопринципные расчеты структуры и электронных свойств двух новых полиморфных разновидностей фторографена были выполнены методом теории функционала плотности. Новые слои фторографена могут формироваться при химической адсорбции фтора на поверхности 5 - 7 графеновых слоев. Структура слоя первого типа более деформирована по сравнению со структурой второго типа (деформационные параметры Def = 60,48° и Def = 31,51° ). Энергии сублимации и ширины запрещенных зон составляют 13,85, 14,17 эВ/(CF), и 4,09, 3,32 эВ для CF - L слоев T1, T2 типов соответственно. First-principle calculations of the structural and electronic properties of two new polymorphic varieties of fluorographene were performed using the density functional theory method. New layers of fluorographene can be formed during chemical adsorption of fluorine on the surface of 5 - 7 graphene layers. The structure of the layer of the first type is more deformed in comparison with the structure of the second type (deformation parameters Def = 60,48 ° and Def = 31,51 °). Sublimation energies and band gaps are 13,85, 14,17 eV/(CF), and 4,09, 3,32 eV for CF-L layers of T1, T 2 types, respectively.

scholarly journals STRUCTURE AND STABILITY OF A TETRAGONAL DIAMOND-LIKE LAYER: FIRST-PRINCIPLE CALCULATIONS

2020 ◽  
pp. 405-414
Author(s):  
Владимир Андреевич Грешняков ◽  
Евгений Анатольевич Беленков
Keyword(s):  
Surface Density ◽  
Density Functional ◽  
Theoretical Study ◽  
Density Functional Theory Method ◽  
First Principle ◽  
Theory Method ◽  
Functional Theory ◽  
First Principle Calculations ◽  
Tetragonal Lattice ◽  
The Density Functional Theory

Методом теории функционала плотности было выполнено теоретическое исследование нового слоевого полиморфа алмаза DL, состоящего из двух полимеризованных тетрагональных графеновых слоев L. Установлено, что новый алмазоподобный слой имеет двумерную тетрагональную решетку с параметром a = b = 0,3822 нм и толщиной 0,1599 нм. Рассчитанные поверхностная плотность и ширина запрещенной зоны этого слоя равны 0,109 мкг/см и 2,63 эВ, соответственно. Новый слой DL должен быть устойчивым, как минимум, до 220 К. Также установлено, что слой DL может быть получен при сильном одноосном сжатии двух графеновых слоев L при давлении 29,6 ГПа. Using the density functional theory method, a theoretical study of a novel layered DL polymorph of diamond, consisting of two polymerized tetragonal graphene L layers, was performed. It was established that the new diamond-like layer has a two-dimensional tetragonal lattice with the parameter a = b = 0,3822 nm and a thickness of 0,1599 nm. The calculated surface density and band gap of this layer are 0,109 μg/cm and 2,63 eV, respectively. The new DL layer must be stable up to at least 220 K. It was also found that the DL layer can be obtained by strong uniaxial compression of two graphene L layers at a pressure of 29,6 GPa.

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.

Electronic structure of the thermoelectric materials PbTe and AgPb18SbTe20 from first-principles calculations

2010 ◽  
Vol 25 (6) ◽  
pp. 1030-1036 ◽  
Author(s):  
Pengxian Lu ◽  
Zigang Shen ◽  
Xing Hu
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Partial Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Scanning Transmission ◽  
Linearized Augmented Plane Wave

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

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