- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Nitrogen Trapping Ability of Hydrogen-Induced Vacancy and the Effect on the Formation of AlN in Aluminum
摘要： This paper presents the ternary interaction of N, H, and vacancy point defects and the nitrogen trapping ability of aluminum vacancies induced by hydrogen by means of DFT methods employed in VASP (Vienna Ab initio Simulation Package) and Abinit packages. The obtained vacancy formation energy of 0.65 eV is close to experimental values. Although the N–vacancy complex is unstable with the negative binding energy of ?0.51 eV, the stability of H–vacancy–N is proved by the positive binding energy of 0.59 eV and the appearance of the orbital hybridization in the density of state (DOS) of atoms connecting to this complex. Moreover, Al vacancies can trap more than 4 N atoms, which prevents the formation of aluminum nitride and subsequently affects not only the hardness of the Al surface but also many practical applications of AlN coating.
关键词： ternary point-defect interaction,first-principles calculations,alpha aluminum,superabundant vacancy
更新于2025-09-09 09:28:46
-
Prediction of Fundamental Properties of Semiconductors and Materials Exploration Using First-Principles Calculations
摘要： 昨今の資源?環境問題やエネルギー情勢を背景に，卓越した機能だけでなく，地球上に豊富に存在する元素により構成され，安価で高い環境調和性を示す新材料が望まれている．社会に役立つ「材料」へと昇華できる新物質を見いだすためには，的確に設計?探索の指針を立てることが重要であることは言うまでもない．そして次の関門が，いかに広い探索空間をカバーするか，その中からどのように有望な物質を絞り込むかである．最近では計算科学の進展とスーパーコンピュータの演算能力の向上により，第一原理計算等の計算科学手法を用いることで物質の安定性や特性を高精度かつ網羅的に予測できるようになってきた．これにデータ科学手法，更にはコンビナトリアル合成?評価等を連携させることで，新物質?新材料の開発を加速し，同時に膨大なデータの解析から設計?探索指針を得ようとする試みが世界各国で盛んになっている．いわゆる「マテリアルズ?インフォマティクス」によるアプローチである．
关键词： surfaces,point defects,interfaces,materials exploration,semiconductors,first-principles calculations
更新于2025-09-09 09:28:46
-
Prediction of two-dimensional organic topological insulator in metal-DCB lattices
摘要： Based on first-principles calculations, we systematically investigated a two-dimensional (2D) organometallic framework consisting of metal atoms (elements from groups IIIA, IVA, VA, VIA, IB, and Pt) and dicyanobenzenes (DCBs). Our stability analysis showed that the system prefers the buckled structure in metals with p-orbital valence electrons, whereas in metals with d-orbitals, the planar phase is preferable. Topological invariants (Z2) of these systems were calculated, and they are identified as 2D intrinsic organic topological insulators. Au- and Bi-DCB are exemplar materials with the largest bandgaps within IB and VA groups. Moreover, Au-DCB exhibits robustness of its topological phase against strain. Furthermore, the topologically protected edge states in Au-DCB are identified to further verify the Z2 invariant. Interestingly, utilizing hole doping in Bi-DCB leads to a nearly flat Chern band and results in the quantum anomalous Hall phase. Our results suggest that these organometallic frameworks are promising for potential applications in quantum spintronics with the merits of low cost and ease of synthesis.
关键词： first-principles calculations,organic topological insulator,quantum spintronics,metal-DCB lattices,two-dimensional
更新于2025-09-09 09:28:46
-
Density Functional Theory Analysis of Electronic and Optical Properties of Two-Dimensional Tantalum Carbides Ta <sub/><i>n</i> +1 </sub> C <i> <sub/>n</sub></i> ( <i>n</i> ?=?1, 2, 3)
摘要： Using first principles methods based on the density functional theory, the electronic structure and optical properties of Ta-containing MXenes (Tant1Cn, n ? 1, 2, 3) are theoretically studied. The results show that the monolayer thickness has a significant effect on the optical properties of Tant1Cn. In the infrared region (<1.6 eV), the thickest Ta4C3 monolayer with seven atomic layers has highest values of absorption coefficients, reflectivity and refraction index. In the visible region, Ta4C3 exhibits different optical characteristics as compared to Ta2C and Ta3C2 due to the different structure configuration and electron interaction. Moreover, a high transmittance over 50% is demonstrated for both Ta2C and Ta3C2, while Ta4C3 monolayer exhibits selectively transmitting feature with a low transmittance of 35% at 1.65 eV and a high transmittance of 84% at 2.25 eV, making Ta4C3 monolayer highly responsive when exposed to visible light and favorable for optical detection.
关键词： tantalum carbides,first-principles calculations,MXenes,optical properties
更新于2025-09-09 09:28:46
-
First-principles study of structural phase transformation and dynamical stability of cubic AlN semiconductors
摘要： Phase transformation and stability of cubic aluminium nitride (AlN) phases such as zinc-blende and rock-salt have been investigated using first-principles calculations based on density functional perturbation theory (DFPT) within quasi-harmonic approximation (QHA). The phonon dispersion relations of both the cubic phases have been calculated at various high-symmetry points of the Brillouin Zone. The pressure and volume dependence of phonon frequencies have been investigated. The application of pressure results in opposite trend of transverse acoustic (TA) phonon frequencies for rock-salt and zinc-blende AlN phases. The TA frequencies found to increase for the former one and decrease for the latter one with the increase in pressure. The dynamical instability results in a volume expansion of rock-salt AlN close to the equilibrium volume of zinc-blende AlN. Phase transformation of these cubic phases is further investigated by computing an equilibrium pressure-temperature phase diagram within QHA. The cubic rock-salt AlN is found to form at high pressures and temperatures than zinc-blende AlN. The temperature dependence of lattice constant and the corresponding volume thermal expansion coefficient of both the cubic phases have been investigated.
关键词： Aluminium nitride,First-principles calculations,Density functional perturbation theory,Quasi-harmonic approximation,Phase transformation,Dynamical stability
更新于2025-09-09 09:28:46
-
[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - A Compact Model of Drift and Diffusion Memristor Applied in Neuron Circuits Design
摘要： A compact model of memristor for unifying two switch characteristics, drift and diffusion has been proposed, based on the ion dynamic transport theory at the oxide interface layer. The model is verified by measured data in different oxide-material-based drift/diffusion memristors, and well fits DC/AC characteristics of both devices, under parameter variations and temperature evolution. Moreover, the applications of this model in neuron circuits design are shown.
关键词： adsorption effect,boron nitride nanotubes,first-principles calculations,small molecule
更新于2025-09-09 09:28:46
-
Visualizing topological edge states of single and double bilayer Bi supported on multibilayer Bi(111) films
摘要： Freestanding single bilayer Bi(111) is a two-dimensional topological insulator with edge states propagating along its perimeter. Given the interlayer coupling experimentally, the topological nature of Bi(111) thin films and the impact of the supporting substrate on the topmost Bi bilayer are still under debate. Here, combined with scanning tunneling microscopy and first-principles calculations, we systematically study the electronic properties of Bi(111) thin films grown on a NbSe2 substrate. Two types of nonmagnetic edge structures, i.e., a conventional zigzag edge and a 2 × 1 reconstructed edge, coexist alternately at the boundaries of single bilayer islands, the topological edge states of which exhibit remarkably different energy and spatial distributions. Prominent edge states are persistently visualized at the edges of both single and double bilayer Bi islands, regardless of the underlying thickness of Bi(111) thin films. We provide an explanation for the topological origin of the observed edge states that is verified with first-principles calculations. Our paper clarifies the long-standing controversy regarding the topology of Bi(111) thin films and reveals the tunability of topological edge states via edge modifications.
关键词： topological insulator,scanning tunneling microscopy,edge states,first-principles calculations,Bi(111) thin films
更新于2025-09-09 09:28:46
-
First-principles study of polar, nonpolar, and semipolar GaN surfaces during oxide vapor phase epitaxy growth
摘要： Stable structures of polar, nonpolar, and semipolar GaN surfaces undergoing oxide vapor phase epitaxy (OVPE) growth were examined with first-principles calculations. The relationships between temperature and pressure growth conditions and stable surface structures are described in surface phase diagrams. The results revealed that an O atom was stably incorporated into the N vacancy site in the N-polar and nonpolar surfaces. The desorption energy of the O atom from the GaN surfaces was estimated to be about 7 eV or higher. This indicates that the O atom did not readily desorb from the GaN surfaces under OVPE growth conditions at 1500 K. The desorption energy from the e000 (cid:2)1T surface was the highest and that from the e10 (cid:2)1 (cid:2)1T surface was the smallest among the calculated values. There was no significant difference in desorption energy among other surfaces.
关键词： first-principles calculations,desorption energy,OVPE,surface phase diagrams,GaN
更新于2025-09-04 15:30:14
-
Electronic structures and optical properties of Fe/Co–doped cubic BaTiO3 ceramics
摘要： The electronic structures and the optical properties of Fe/Co–doped cubic BaTiO3 ceramics in which the Ti sites replaced partly and uniformly by Fe or Co chemical elements have been investigated using first–principles method based on the density functional theoretical framework. The calculated energy band structures indicate that Fe/Co–doped cubic BaTiO3 system has electrically conductivity while the purely BaTiO3 features the characteristic of semi–conductivity. In consistent with the energy band structures, some new peaks correlated to the impurity bands have arisen in the total density of state of the Fe/Co–doped BaTiO3 system due to the 3d orbital of Fe/Co atoms making an evidently contribution and a strong orbital hybridization incurred by d–d interaction and p–d interaction near the Fermi energy level being introduced by Fe/Co–doping. The analysis of optical properties, including the calculation of dielectric function, reflection spectrum and absorption spectrum of Fe/Co–doped BaTiO3 system, implied that their photoelectric properties can be improved by Fe/Co–doping due to the required activation energy for the photoelectron transition being reduced effectively. These phenomena such as red–shift phenomenon, the bridge effect of impurity bands and the strong orbital hybridization suggested that they can be as a potentially candidate for optoelectronic materials applied in the field of energy conversion.
关键词： Cubic BaTiO3,Fe/Co–doping,Optical properties,First–principles calculations
更新于2025-09-04 15:30:14
-
First-Principles Insights into the Oxidation States and Electronic Structures of Ceria-Based Binary, Ternary and Quaternary Oxides
摘要： Ceria and ceria-based materials have versatile technological and industrial applications, physically ascribed to the flexible fluctuation of Ce oxidation state between Ce4+ and Ce3+. A considerable multi-disciplinary research has been spent to obtain Ce oxidation state, the crucial quantity regarding the application; however, a rigorous and physically correct determination of oxidation state is still lacking. Here we conduct first-principles DFT + U calculations to unambiguously determine the physical oxidation state of Ce in ceria-based materials such as the homogenous CenO2n-2 (n = 7, 9, 10, 11, 12), ceria doped by multivalent Ti and V, Ce-Ti(V)-O ternary compounds, and Ce-Ti-V-O quaternary compounds. The results show that Ce oxidation state depends on the local structure and chemical surrounding: Oxygen vacancy facilitates the transition from Ce4+ to Ce3+, consistent with the localization of Ce 4f electrons; Ti and V with the 3d energy levels higher than 4f energy levels of Ce generally tend to reduce Ce4+ to Ce3+ particularly under the oxygen-deficiency condition. The atom-resolved determination of Ce oxidation states in the complicated compounds offers great promise for understanding the physical and chemical behavior of ceria-based materials, and for rational design of novel ceria-based materials for application potentials.
关键词： Ceria-based materials,First-principles calculations,Electronic structures,DFT + U,Oxidation states
更新于2025-09-04 15:30:14