First-principles Investigation of Edged Ferroelectric PbTiO3 Nanowires and the Role of Axial Strain

2009 ◽  
Vol 1199 ◽  
Author(s):  
Takahiro Shimada ◽  
Shogo Tomoda ◽  
Takayuki Kitamura
Keyword(s):  
Cross Section ◽  
First Principles ◽  
Electronic Structures ◽  
Axial Strain ◽  
Covalent Bond ◽  
First Principles Calculations ◽  
Significant Suppression ◽  
Axial Tension ◽  
Sharp Edges

AbstractAtomistic and electronic structures of PbTiO3 nanowires with atomically sharp edges consisting of (100)/(010) surfaces using first-principles calculations. Ferroelectricity is enhanced at the PbO-terminated edge in the nanowire because the Pb-O covalent bond that predominates the ferroelectric distortions is partially strengthened. On the other hand, a significant suppression is observed in the TiO2-terminated nanowire. Surprisingly, the smallest (one-unit-cell cross- section) PbO-terminated nanowire can keep ferroelectricity, while ferroelectricity disappears in the TiO2-terminated nanowires with a diameter of smaller than 17 Å. The ferroelectricity is recovered by axial tension, where the thinner nanowire requires the higher critical strain.

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.

Magnetism and electronic structures of bismuth (stannum) films at the CrI3 (CrBr3) interface

2021 ◽  
Vol 23 (7) ◽  
pp. 4255-4261
Author(s):  
Li Chen ◽  
Chuan Jiang ◽  
Maoyou Yang ◽  
Tao Hu ◽  
Yan Meng ◽  
...  
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
First Principles Calculations

From first-principles calculations, the magnetism and electronic structures of bilayer bismuth (stannum) films at the monolayer CrI3 (CrBr3) interface are studied.

An effective and efficient approach to p-type AlN by Be2:O codoping from first-principles calculations

2016 ◽  
Vol 30 (20) ◽  
pp. 1650257
Author(s):  
Meng Zhao ◽  
Wenjun Wang ◽  
Jun Wang ◽  
Junwei Yang ◽  
Weijie Hu ◽  
...  
Keyword(s):  
First Principles ◽  
Ionization Energy ◽  
Hole Concentration ◽  
Valence Band Maximum ◽  
First Principles Calculations ◽  
Mutual Compensation ◽  
Efficient Approach ◽  
P Type ◽  
Codoping Method

Various Be:O-codoped AlN crystals have been investigated via first-principles calculations to evaluate the role of the different combinations in effectively and efficiently inducing p-type carriers. It is found that the O atom is favored to bond with two Be atoms. The formed Be2:O complexes decrease the acceptor ionization energy to 0.11 eV, which is 0.16 eV lower than that of an isolated Be in AlN, implying that the hole concentration could probably be increased by 2–3 orders of magnitude. The electronic structure of Be2:O-codoped AlN shows that the lower ionization energy can be attributed to the interaction between Be and O. The Be–O complexes, despite failing to induce p-type carriers for the mutual compensation of Be and O, introduce new occupied states on the valence-band maximum (VBM) and hence the energy needed for the transition of electrons to the acceptor level is reduced. Thus, the Be2:O codoping method is expected to be an effective and efficient approach to realizing p-type AlN.

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.

Stability and Structures of Constitutional Defects in Nonstoichiometric Intermetallic Compounds by First-Principles Calculations

2005 ◽  
Vol 475-479 ◽  
pp. 3111-3114
Author(s):  
Masataka Mizuno ◽  
Hideki Araki ◽  
Yasuharu Shirai
Keyword(s):  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Stoichiometric Composition ◽  
Electronic Structure Calculations ◽  
First Principles Calculations ◽  
Compositional Dependence ◽  
Wide Range ◽  
Formation Energies ◽  
Structure Calculations

Some of intermetallic compounds exist in a wide range of concentration around the stoichiometric composition. First-principles electronic structure calculations have been performed for constitutional defects in non-stoichiometric CoAl and CoTi in order to investigate their stabilities and structural relaxations induced by constitutional defects. For the evaluation of stabilities of constitutional defects, the compositional dependence curves both of formation energies and of lattice parameters are obtained by the calculations employing supercells in various sizes. The lattice relaxations around constitutional defects are discussed by analyzing the change in electronic structures induced by constitutional defects.

Computational and Experimental Insights into the Role of Acidic Molecules on the Corrosion Behavior on 7A46 Aluminum Alloy

2021 ◽  
Vol 21 (4) ◽  
pp. 2221-2233
Author(s):  
Yaru Liu ◽  
Qinglin Pan ◽  
Xiangdong Wang ◽  
Ye Ji ◽  
Qicheng Liu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Corrosion Behavior ◽  
First Principles ◽  
First Principles Calculations ◽  
Corrosive Media ◽  
Corrosion Depth ◽  
Corrosion Mechanisms ◽  
Nanoscale Level

The corrosion mechanisms for different corrosive media on the aged 7A46 aluminum alloy were systematically investigated at nanoscale level. The combination of empirical intergranular and exfoliation corrosion behavior was employed, and coupled with first-principles calculations. Results revealed that the dispersed distribution of matrix precipitates (MPs) leads to the enhancement of the corrosion resistance pre-ageing (PA) followed by double-ageing (PA-DA) alloy. The deepest corrosion depth of PA-DA alloy was in hydrochloric acid, and the calculation result demonstrates that the passivation effect in combination with the accumulation of corrosion products in nitric acid protect the PA-DA alloy from further corrosion.

First-Principles Calculations of Titanium Dopants in Alumina

2005 ◽  
Vol 475-479 ◽  
pp. 3095-3098
Author(s):  
Katsuyuki Matsunaga ◽  
Teruyasu Mizoguchi ◽  
Atsutomo Nakamura ◽  
Takahisa Yamamoto ◽  
Yuichi Ikuhara
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
First Principles Calculations ◽  
Pseudopotential Calculations ◽  
Formation Energies

First-principles pseudopotential calculations were performed to investigate atomic and electronic structures of titanium (Ti) dopants in alumina (Al2O3). It was found that a substitutional Ti3+ defect induced an extra level occupied by one electron within the band gap of Al2O3. When two or more substitutional Ti3+ defects were located closely to each other, the defect-induced levels exhibited strong bonding interactions, and their formation energies decreased with increasing numbers of Ti3+ defects. This indicates that association and clustering of substitutional Ti3+ defects in Al2O3 can take place due to the interaction of the defect-induced levels.

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