ACCEPTOR MODULATED DEFECT AND ELECTRONIC STRUCTURES IN FERROELECTRIC LEAD TITANATE: AN AB INITIO STUDY

2008 ◽  
Vol 01 (02) ◽  
pp. 121-126 ◽  
Author(s):  
ZHEN ZHANG ◽  
PING WU ◽  
LI LU ◽  
CHANG SHU
Keyword(s):  
Electronic Structures ◽  
Defect Structure ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Charge Effects ◽  
Isolated Point ◽  
Point Defect Structure ◽  
Domain Pinning

Defects and electronic structures of the aliovalent acceptors substituted lead titanates were studied using density functional theory calculations. Three types of defect structures are identified in 3d transition metal and the group IIB and VB elements substituted systems. Cr substitute and oxygen vacancies are found to be dissociated from each other, forming an isolated point defect structure. In contrast, all other substitutes favor the immobile acceptor–oxygen–vacancy–acceptor defect clusters which weaken the space charge effects by limiting the motions of oxygen vacancies. Furthermore, two distinct defect-cluster structures (along the z direction and in the xy plane, respectively) are observed. We conclude that the defect structure in the xy plane induces head-to-head polarization patterns, which make the domain pinning effects even weaker. The electronic structures due to elements substitutions are also investigated and compared.

scholarly journals Study on the adsorption selection of CH$$_4$$ on CuO (110) versus (111) surfaces: a density functional theory study

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Long Lin ◽  
Linwei Yao ◽  
Shaofei Li ◽  
Zhengguang Shi ◽  
Kun Xie ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Adsorption Capacity ◽  
Active Sites ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Density Functional Theory Calculations ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Strong Adsorption ◽  
Selection Of

AbstractFinding the active sites of suitable metal oxides is a key prerequisite for detecting CH$$_4$$ 4 . The purpose of the paper is to investigate the adsorption of CH$$_4$$ 4 on intrinsic and oxygen-vacancies CuO (111) and (110) surfaces using density functional theory calculations. The results show that CH$$_4$$ 4 has a strong adsorption energy of −0.370 to 0.391 eV at all site on the CuO (110) surface. The adsorption capacity of CH$$_4$$ 4 on CuO (111) surface is weak, ranging from −0.156 to −0.325 eV. In the surface containing oxygen vacancies, the adsorption capacity of CuO surface to CH$$_4$$ 4 is significantly stronger than that of intrinsic CuO surface. The results indicate that CuO (110) has strong adsorption and charge transfer capacity for CH$$_4$$ 4 , which may provide experimental guidance.

Probing the electronic structures of Con (n = 1–5) clusters on γ-Al2O3 surfaces using first-principles calculations

2017 ◽  
Vol 19 (5) ◽  
pp. 3679-3687 ◽  
Author(s):  
Tao Yang ◽  
Masahiro Ehara
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
First Principles Calculations ◽  
Functional Theory

Using density functional theory calculations, we discussed the geometric and electronic structures and nucleation of small Co clusters on γ-Al2O3(100) and γ-Al2O3(110) surfaces.

Density functional theory calculations of atomic, electronic and thermodynamic properties of cubic LaCoO3and La1−xSrxCoO3surfaces

RSC Advances ◽  
2015 ◽  
Vol 5 (1) ◽  
pp. 760-769 ◽  
Author(s):  
Shuguang Zhang ◽  
Ning Han ◽  
Xiaoyao Tan
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Phase Diagrams ◽  
Thermodynamic Stability ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Spin Polarized

Spin-polarized DFT calculations were used to investigate the atomic, electronic structures of LaCoO3and La1−xSrxCoO3surfaces. The thermodynamic stability of these surfaces was analyzed with phase diagrams. Influence of Sr-doping was also examined.

scholarly journals A First-Principles Exploration of NaxSy Binary Phases at 1 atm and Under Pressure

Crystals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 441 ◽  
Author(s):  
Nisha Geng ◽  
Tiange Bi ◽  
Niloofar Zarifi ◽  
Yan Yan ◽  
Eva Zurek
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elemental Sulfur ◽  
Density Functional Theory Calculations ◽  
Metastable Phases ◽  
Van Der Waals Interactions ◽  
Two Dimensional ◽  
Functional Theory ◽  
Battery Materials

Interest in Na-S compounds stems from their use in battery materials at 1 atm, as well as the potential for superconductivity under pressure. Evolutionary structure searches coupled with Density Functional Theory calculations were employed to predict stable and low-lying metastable phases of sodium poor and sodium rich sulfides at 1 atm and within 100–200 GPa. At ambient pressures, four new stable or metastable phases with unbranched sulfur motifs were predicted: Na2S3 with C 2 / c and Imm2 symmetry, C 2 -Na2S5 and C 2 -Na2S8. Van der Waals interactions were shown to affect the energy ordering of various polymorphs. At high pressure, several novel phases that contained a wide variety of zero-, one-, and two-dimensional sulfur motifs were predicted, and their electronic structures and bonding were analyzed. At 200 GPa, P 4 / m m m -Na2S8 was predicted to become superconducting below 15.5 K, which is close to results previously obtained for the β -Po phase of elemental sulfur. The structures of the most stable M3S and M4S, M = Na, phases differed from those previously reported for compounds with M = H, Li, K.

scholarly journals Enhancement of Titania Photoanode Performance by Sandwiching Copper between Two Titania Layers

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4326
Author(s):  
Fan Yang ◽  
Ruizhuang Yang ◽  
Lin Yan ◽  
Jiankun Wu ◽  
Xiaolin Liu ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Sandwich Structure ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Light Response ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Tio2 Lattice ◽  
Novel Method ◽  
Cu Dopant

Vacancies in semiconductors can play a versatile role in boosting their photocatalytic activity. In this work, a novel TiO2/Cu/TiO2 sandwich structure is designed and constructed. Abundant vacancies were introduced in TiO2 lattice by Cu reduction under heat treatment. Meanwhile, Cu atom could diffuse into TiO2 to form Cu-doped TiO2. The synergistic effect between oxygen vacancies and Cu atoms achieved about 2.4 times improved photocurrent of TiO2/Cu/TiO2 sandwich structure compared to bare TiO2 thin film. The enhanced photoactivity may be attributed to regulated electron structure of TiO2 by oxygen vacancies and Cu dopant from experimental results and density functional theory calculations. Oxygen vacancies and Cu dopant in TiO2 formed through copper metal reduction can introduce impurity levels and narrow the band gap of TiO2, thus improve the visible light response. More importantly, the Cu2+ and oxygen vacancies in TiO2 lattice can dramatically increase the charge density around conduction band and promote separation of photo-induced charge carriers. Furthermore, the oxygen vacancies on the surface may serve as active site for sufficient chemical reaction. This work presents a novel method to prepare doped metal oxides catalysts with abundant vacancies for improving photocatalytic activity.

scholarly journals Computational investigation of Zn-doped and undoped SrEu2Fe2O7 as potential mixed electron and proton conductors

RSC Advances ◽  
2020 ◽  
Vol 10 (66) ◽  
pp. 39988-39994
Author(s):  
Zongzi Jin ◽  
Ranran Peng ◽  
Yunpeng Xia ◽  
Zhenbin Wang ◽  
Wei Liu
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Oxygen Vacancies ◽  
Density Functional Theory Calculations ◽  
Proton Conductors ◽  
Computational Investigation ◽  
Functional Theory ◽  
Proton Defects

Density functional theory calculations are employed to investigate the formation and conducting behaviors of oxygen vacancies and proton defects in Ruddlesden–Popper oxide SrEu2Fe2O7.

scholarly journals Annealing effects on the structural and dielectric properties of (Nb + In) co-doped rutile TiO2 ceramics

RSC Advances ◽  
2019 ◽  
Vol 9 (15) ◽  
pp. 8364-8368 ◽  
Author(s):  
Lanling Zhao ◽  
Jun Wang ◽  
Zhigang Gai ◽  
Jichao Li ◽  
Jian Liu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dielectric Properties ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Rutile Tio2 ◽  
Annealing Effects ◽  
Co Doped

Density functional theory calculations were conducted to investigate the electronic structures of rutile Ti16O32, Ti13Nb2InO32, and Ti13Nb2InO31 systems.

First-principles study on codoping effect to enhance photocatalytic activity of anatase TiO2

2017 ◽  
Vol 31 (06) ◽  
pp. 1750036
Author(s):  
Yujie Bai ◽  
Qinfang Zhang ◽  
Fubao Zheng ◽  
Yun Yang ◽  
Qiangqiang Meng ◽  
...  
Keyword(s):  
Visible Light ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Energy Gap ◽  
Density Functional Theory Calculations ◽  
Band Edge ◽  
Electron Hole ◽  
Functional Theory ◽  
Rich Condition

Codopant is an effective approach to modify the bandgap and band edge positions of transition metal oxide. Here, the electronic structures as well as the optical properties of pristine, mono-doped (N/P/Sb) and codoped (Sb, N/P) anatase TiO2 have been systematically investigated based on density functional theory calculations. It is found that mono-doped TiO2 exhibits either unoccupied or partially occupied intermediate state within the energy gap, which promotes the recombination of electron-hole pairs. However, the presence of (Sb, N/P) codopant not only effectively reduces the width of bandgap by introducing delocalized occupied intermediate states, but also adjusts the band edge alignment to enhance the hydrogen evolution activity of TiO2. Moreover, the optical absorption spectrum for (Sb, N/P) codoped TiO2, which is favored under oxygen-rich condition, demonstrates the improvement of its visible light absorption. These findings will promote the potential application of (Sb, N/P) codoped TiO2 photocatalysis for water splitting under visible light irradiation.

Novel visible-light sensitive vanadate photocatalysts for water oxidation: implications from density functional theory calculations

2015 ◽  
Vol 3 (20) ◽  
pp. 10720-10723 ◽  
Author(s):  
Peng Li ◽  
Naoto Umezawa ◽  
Hideki Abe ◽  
Jinhua Ye
Keyword(s):  
Density Functional Theory ◽  
Visible Light ◽  
Water Oxidation ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Oxidation Reactions ◽  
Functional Theory

New vanadate photocatalysts, Ag2Sr(VO3)4 and Sr(VO3)2, are theoretically designed for water oxidation reactions. The calculations have shown that the new photocatalysts possess desirable electronic structures. Our experiments demonstrated that these vanadates efficiently oxidize water to O2 under irradiation of visible light.

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