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Dislocation neutralizing in a self-organized array of dislocation and anti-dislocation

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Chinese physics B 2019年第11期28卷 251-257页

作者：邓凤麟胡湘生王少峰 department of physics and institute for structure and function Chongqing UniversityChongqing 400030China department of Mechanics Huazhong University of Science and TechnologyWuhan 430074China

A one-dimensional(1 D) self-organized array composed of dislocation and anti-dislocation is analytically investigated in the frame of Peierls theory. From the exact solution of the Peierls equation, it is found that there exists strong neutralizing effect that makes the Burgers vector of each individual dislocation in the equilibrium array smaller than that of an isolated dislocation. This neutralizing effect is not negligible even though dislocations are well separated. For example, when the distance between the dislocation and the anti-dislocation is as large as ten times of the dislocation width, the actual Burgers vector is only about 80% of an isolated dislocation. The neutralizing effect originates physically from the power-law asymptotic behavior that enables two dislocations interfere even though they are well separated.

关键词： dislocation array neutralizing exact solution

一种新型铬基砷化物La3CrAs5的高压合成、结构表征及物性研究

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Science China Materials 2020年第9期63卷 1750-1758页

作者：段磊望贤成詹方洋张俊胡志伟赵建发李文敏曹立朋邓正于润泽林宏基 Chien-Te.Chen 王锐靳常青 Beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190 School of physics University of Chinese Academy of SciencesBeijing 100190 institute for structure and function&department of physics Chongqing UniversityChongqing 400044 Max Plank institute for Chemical physics of Solids Dresden D-01187 National Synchrotron Radiation Research Center Hsinchu 30076 Materials Research Lab at Songshan Lake Dongguan 523808

本文中,我们利用高温高压法,在La-Cr-As体系中发现并成功制备了第一个新的三元化合物材料La3CrAs5.该化合物属于六方反Hf5Sn3Cu型结构,其空间群为P3/mcm,晶格参数为a=b=8.9845A,c=5.8897A.La3CrAs5的晶体结构含有沿c轴方向的共面连接Cr... 详细信息

本文中,我们利用高温高压法,在La-Cr-As体系中发现并成功制备了第一个新的三元化合物材料La3CrAs5.该化合物属于六方反Hf5Sn3Cu型结构,其空间群为P3/mcm,晶格参数为a=b=8.9845A,c=5.8897A.La3CrAs5的晶体结构含有沿c轴方向的共面连接CrAs6八面体链,这些一维自旋链在ab平面内以三角格子形式进行排列,链与链之间的距离为8.9845A.研究表明,La3CrAs5具有三维金属导电性质,并且在低温条件下遵循费米液行为;另外,La3CrAs5中CrAs6自旋链由于巡游电子关联,在50K发生三维铁磁相变.理论计算表明,La对费米面附近态密度的贡献是不可忽略的,导致La3CrAs5成为了一个三维金属.此外,我们还计算了晶体轨道哈密顿数(-COHP)来解释La3CrAs5结构的整体稳定性以及化学键特征.

关键词： Cr-based arsenide ferromagnetic metal high pressure synthesis spin chain

Thermal and radiative characteristics of oxyfluoride glass singly doped with lanthanide ions

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Journal of Rare Earths 2010年第6期28卷 893-898页

作者： Barbara KLIMESZ Grazyna DOMINIAK-DZIK Witold RYBA-ROMANOWSKI department of physics Opole University of Technology institute of Low Temperature and structure Research Polish Academy of Sciences

Rare earths-doped oxyfluoride glasses based on germanium oxide and lead fluoride were prepared from commercial raw materials. The glasses with general composition of 50GeO2-(50-x-y)PbO-yPbF2-xLnF3 (Ln=Pr3+-Yb3+), contained different concentrations of optically active dopants (x=0.2 mol.% and 2 mol.%) and PbF2 (y≤15 mol.%). The differential thermal analysis (DTA) was used to determine both thermal characteristic and thermal stability properties of the glasses in the function of the kind of dopant, its concentration, and a glass composition. Characteristic glass temperatures such as glass transition temperature (Tg), glass crystallization temperature (Tc) and temperature corresponding to the maximum of the crystallization rate (Tpc) were evaluated. On the basis of obtained results, the thermal stabilities of glasses under study were evaluated using various thermal stability criteria (Dietzel factor ?T, Saad-Poulain factors H’ and S). It was found that the increase in rare earth fluoride contents influenced thermal characteristics when the characteristic temperatures of the individual glass was shifted towards higher values. The effect of the PbF2 content and the kind of rare earth impurity on the glass stability was observed. Absorption spectra of lanthanide-doped glasses were measured at room temperature and used to determine the phenomenological intensity parameters Ωt and next, to estimate radiative properties of lanthanide ions in this matrix. Radiative transition probabilities of luminescent states of Ln3+, branching ratios and radiative lifetimes were determined. The variation of the Ωt along the lanthanide series was presented and discussed.

关键词： oxyfluoride glasses rare earths DTA thermal stability of glasses radiative transition probabilities radiative lifetimes

Pyridinic-N doping carbon layers coupled with tensile strain of FeNi alloy for activating water and urea oxidation

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Green Energy & Environment 2024年第4期9卷 684-694页

作者： Guangfu Qian Wei Chen Jinli Chen Li Yong Gan Tianqi Yu Miaojing Pan Xiaoyan Zhuo Shibin Yin Guangxi Key Laboratory of Electrochemical Energy Materials College of Chemistry and Chemical EngineeringState Key Laboratory of Processing for Non-Ferrous Metal and Featured MaterialsGuangxi University100 Daxue RoadNanning530004China institute for structure and function and department of physics Chongqing UniversityChongqing400030China

Exploitation of oxygen evolution reaction(OER)and urea oxidation reaction(UOR)catalysts with high activity and stability at large current density is a major challenge for energy-saving H_(2) production in water electrolysis.Herein,we use the pyridinic-N doping carbon layers coupled with tensile strain of FeNi alloy activated by NiFe_(2)O_(4)(FeNi/NiFe_(2)O_(4)@NC)for efficiently increasing the performance of water and urea oxidation.Due to the tensile strain effect on FeNi/NiFe_(2)O_(4)@NC,it provides a favorable modulation on the electronic properties of the active center,thus enabling amazing OER(η_(100)=196 mV)and UOR(E_(10)=1.32 V)intrinsic activity.Besides,the carbon-coated layers can be used as armor to prevent FeNi alloy from being corroded by the electrolyte for enhancing the OER/UOR stability at large current density,showing high industrial practicability.This work thus provides a simple way to prepare high-efficiency catalyst for activating water and urea oxidation.

关键词： Carbon-encapsulated Tensile strain Catalyst Oxygen evolution reaction Urea oxidation reaction

Core structure and Peierls stress of the 90°dislocation and the 60°dislocation in aluminum investigated by the fully discrete Peierls model

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Chinese physics B 2022年第8期31卷 517-529页

作者：向浩王锐邓凤麟王少峰 department of physics and institute for structure and function Chongqing UniversityChongqing 401331China CAS Key Laboratory of Magnetic Materials and Devices Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China

The core structure,Peierls stress and core energy,etc.are comprehensively investigated for the 90°dislocation and the 60°dislocation in metal aluminum using the fully discrete Peierls model,and in particular thermal effects are included for temperature range 0≤T≤900 K.For the 90°dislocation,the core clearly dissociates into two partial dislocations with the separating distance D~12?,and the Peierls stress is very smallσpstructures is weak for both the 90°dislocation and the 60°dislocation.The core structures theoretically predicted at T=0 K are also confirmed by the first principle simulations.

关键词： dislocation temperature effect aluminum

Electronic structures and strengthening mechanisms of superhard high-entropy diborides

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稀有金属：英文版 2023年第2期42卷 614-628页

作者： Gang Yao William-Yi Wang Pei-Xuan Li Ke Ren Jia-Qi Lu Xing-Yu Gao De-Ye Lin Jun Wang Yi-Guang Wang Hai-Feng Song Zi-Kui Liu Jin-Shan Li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China Innovation Center NPU ChongqingChongqing401135China Laboratory of Computational physics Institute of Applied Physics and Computational MathematicsBeijing100088China institute of Advanced structure Technology Beijing Institute of TechnologyBeijing100081China department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA16802USA

High-entropy diborides(HEBs)have attracted extensive research due to their potential ultra-high hardness.In the present work,the effects of transition metals(TM)on lattice parameters,electron work function(EWF),bonding charge density,and hardness of HEBs are comprehensively investigated by the first-principles calculations,including(TiZrHfNbTa)B_(2),(TiZrHfNbMo)B_(2),(TiZrHfTaMo)B_(2),(TiZrNbTaMo)B_(2),and(TiHfNbTaMo)B_(2).It is revealed that the disordered TM atoms result in a severe local lattice distortion and the formation of weak spots.In view of bonding charge density,it is understood that the degree of electron contribution of TM atoms directly affects the bonding strength of the metallic layer,contributing to the optimized hardness of HEBs.Moreover,the proposed power-law-scaled relationship integrating the EWF and the grain size yields an excellent agreement between our predicted results and those reported experimental ones.It is found that the HEBs exhibit relatively high hardness which is higher than those of single transition metal diborides.In particular,the hardness of(TiZrNbTaMo)B_(2)and(TiHfNbTaMo)B_(2)can be as high as29.15 and 28.02 GPa,respectively.This work provides a rapid strategy to discover/design advanced HEBs efficiently,supported by the coupling hardening mechanisms of solid solution and grain refinement based on the atomic and electronic interactions.

关键词： High-entropy diborides(HEBs) Hardness Electronic structure Lattice distortion Power-law

Omnidirectional iridescence via cylindricallypolarized femtosecond laser processing

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Opto-Electronic Advances 2020年第5期3卷 11-18页

作者： Nikolaos Livakas Evangelos Skoulas Emmanuel Stratakis institute of Electronic structure and Laser Foundation for Research and Technology-HellasHeraklion Crete 71110Greece department of Materials Science and Technology University of CreteHeraklion Crete 71003Greece department of physics University of CreteHeraklion Crete 71003Greece

We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is realized by means of multi-directional low-spatial-frequency,laser-induced periodic surface structures(LSFL)formed upon exploiting the cylindrical symmetry of a cylindrical vector(CV)fs field.We particularly demonstrate that the multi-directional gratings formed on stainless steel surface by a radially polarized fs beam,could mimic the omnidirectional structural coloration properties found in some natural species.Accordingly,the fabricated grating structures can spatially disperse the incident light into individual wavelength with high efficiency,exhibiting structural iridescence at all viewing angles.Analytical calculations using the grating equation reproduced the characteristic variation of the vivid colors observed as a function of incident angle.We envisage that our results will significantly contribute to the development of new photonic and light sensing devices.

关键词： laser processing structural colors radial polarisation

Ground-State structure and Physical Properties of NB_2 Predicted from First Principles

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Chinese physics Letters 2016年第3期33卷 78-81页

作者：吴旌贺刘长欣 department of physics Henan Institute of Education

Using the newly developed particle swarm optimization algorithm on crystal structural prediction, we predict a new class of boron nitride with stoicMometry of NB2 at ambient pressure, which belongs to the tetragonal 14m2 space group. Then, its structure, elastic properties, electronic structure, and chemical bonding are investigated by first-principles calculations with the density functional theory. The phonon calculation and elastic constants confirm that the predicted NB2 is dynamically and mechanically stable, respectively. The large bulk modulus, large shear modulus, large Young＇s modulus, and small Poisson＇s ratio show that the 14m2 NB2 should be a new superhard material with a calculated theoretical Vickers hardness value of 66 GPa. Further analysis on density of states and electron localization function demonstrate that the strong B B and 13 N covalent bonds are the main reason for its high hardness in 14m2 NB2.

关键词： NB is in of Ground-State structure and Physical Properties of NB2 Predicted from First Principles from

From Discreteness to Continuity： Dislocation Equation for Two-Dimensional Triangular Lattice

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Chinese physics Letters 2007年第1期24卷 143-146页

作者：王少峰 institute for structure and function Chongqing University Chongqing 400044

到连续性的从组件的一个系统的方法为三角形的格子的脱臼方程被介绍。Peierls 方程的修正严格地被导出。修改方程包括为脱臼的核心结构重要的分离效果的更高的顺序修正。修改方程拥有除了因素，模型无关的一种通用形式，这被观察。因素... 详细信息

到连续性的从组件的一个系统的方法为三角形的格子的脱臼方程被介绍。Peierls 方程的修正严格地被导出。修改方程包括为脱臼的核心结构重要的分离效果的更高的顺序修正。修改方程拥有除了因素，模型无关的一种通用形式，这被观察。因素，取决于模型的详细，与在在波浪向量空间的它的零个点的核的衍生物有关。结果打开一个方法因为一个人需要到的，确实是在波浪向量空格在内核的零个点附近调查行为而不是完全计算内核，应付复杂模特儿。

关键词：位错方程式三角晶格物理学计量方法