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Study on H atoms diffusion and adsorption properties of MgH_2-V systems

Science china(Technological Sciences) 2008年第7期51卷 979-988页

作者： zhou dianwu1,2, liu jinshui3.& peng ping3.1 state key laboratory of advanced design and manufacturing for vehicle body, hunan university, changsha 410082, china 2 College of Mechanical and Automatic Engineering, hunan university, changsha 410082, china 3 College of Materials Science and Engineering, hunan university, changsha 410082, china 1. state key laboratory of advanced design and manufacturing for vehicle body Hunan University Changsha 410082 China 2. College of Mechanical and Automatic Engineering Hunan University Changsha 410082 China 3. College of Materials Science and Engineering Hunan University Changsha 410082 China

Based on experimental results that VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH2-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH2 interface is formed due to V alloying MgH2 phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH2 phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH2-V systems is reduced compared with that of MgH2 phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH2 across VH/MgH2 interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH2 phase region.

关键词： plane-wave pseudopotential theory magnesium hydride diffusion adsorption

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LiNH_2-X(X=Mg,Al,Ti,Nb)体系解氢性能的第一原理计算

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化学学报 2011年第14期69卷 1715-1720页

作者：袁江周惦武彭平侯德政湖南大学汽车车身先进设计制造国家重点实验室长沙410082 湖南张家界航空工业职业技术学院张家界427000

采用基于密度泛函理论的第一原理赝势平面波方法,计算了LiNH2-X(X=Mg,Al,Ti,Nb)体系的晶体与电子结构及稳定性能.负合金形成热与H原子解离能的计算发现:合金化元素X在LiNH2中少量置换固溶时,体系结构稳定性发生变化,合金化增强了体系的... 详细信息

采用基于密度泛函理论的第一原理赝势平面波方法,计算了LiNH2-X(X=Mg,Al,Ti,Nb)体系的晶体与电子结构及稳定性能.负合金形成热与H原子解离能的计算发现:合金化元素X在LiNH2中少量置换固溶时,体系结构稳定性发生变化,合金化增强了体系的解氢能力,其中Nb提高LiNH2体系解氢效果最好,理论计算预测合金化提高体系解氢性能与他人结果一致.电子态密度(DOS)与电子密度分析发现:X(X=Mg,Al,Ti,Nb)合金化提高LiNH2解氢能力的主要原因是X导致LiNH2体系Fermi能级附近能隙值发生变化以及Li与NH之间的成键作用减弱.

关键词：赝势平面波 LiNH2 合金形成热电子结构

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LiBH_4-X(X=O,F和Cl)体系解氢性能的第一原理计算

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化学学报 2012年第1期70卷 71-77页

作者：李闯周惦武彭平万隆湖南大学汽车车身先进设计制造国家重点实验室长沙410082 湖南大学材料科学与工程学院长沙410082

采用基于密度泛函理论的第一原理方法,计算了LiBH4-X(X=O,F和Cl)体系的晶体与电子结构及解氢性能.生成热和H原子解离能的计算结果表明:O原子掺杂优先占据LiBH4间隙位,F置换氢原子位,而Cl则取代BH4单元;O,F和Cl掺杂的LiBH4体系结构稳定... 详细信息

采用基于密度泛函理论的第一原理方法,计算了LiBH4-X(X=O,F和Cl)体系的晶体与电子结构及解氢性能.生成热和H原子解离能的计算结果表明:O原子掺杂优先占据LiBH4间隙位,F置换氢原子位,而Cl则取代BH4单元;O,F和Cl掺杂的LiBH4体系结构稳定性发生变化,其中O提高体系解氢效果明显,而F和Cl掺杂受H原子区域环境的影响.态密度、Mulliken电子占据数和电子密度的分析结果表明:B—H之间较强的共价键是LiBH4结构稳定、解氢困难的电子结构根源,O,F和Cl对LiBH4解氢能力影响主要是掺杂改变了H的s态与B的sp态的杂化特性、以及BH4单元与Li的成键作用.

关键词：第一原理计算 LiBH4 解氢能力电子结构

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First-principles and experimental investigations on ductility/brittleness of intermetallic compounds and joint properties in steel/aluminum laser welding

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Transactions of Nonferrous Metals Society of china 2021年第10期31卷 2962-2977页

作者： Tian LI Dian-wu zhou You-rui-ling YAN ping peng Jin-shui liu state key laboratory of advanced design and manufacturing for vehicle body Hunan UniversityChangsha 410082China School of Materials Science and Engineering Hunan UniversityChangsha 410082China

Morphology,distribution,composition,forming ability,structural stability and intrinsic mechanical properties of the intermetallic compounds(IMCs)formed in steel/aluminum laser welding were determined through scanning electron microscope,energy dispersive spectrometer,X-ray diffractometer and first-principles *** was found that the mechanical properties of the joint are limited by the Fe−Al IMCs,whose brittleness is attributed to the orbital hybridization between Al(s),Al(p)and Fe(d).However,the joint properties are improved by adding interlayer,which is ascribed to some changes of electronic structure of the generated *** transition mechanism of IMCs changing from brittle to ductile is mainly due to the weak ability of interlayer elements to attract *** mechanical properties of the joint are closely related to the ductility or brittleness of the ***,the addition of Ti foil interlayer effectively improves the mechanical properties of the joints,which means that the experimental verification is in good agreement with the theoretical calculation predictions.

关键词： first-principles calculation elastic constant ductility brittleness laser welding mechanical properties

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A first-principles study on electronic structure and elastic properties of Al_4Sr, Mg_2Sr and Mg_(23)Sr_6 phases

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Transactions of Nonferrous Metals Society of china 2011年第12期21卷 2677-2683页

作者：周惦武刘金水彭平湖南大学汽车车身先进设计制造国家重点实验室长沙410082

The electronic structures and mechanical properties of Al4Sr, Mg2Sr and Mg23Sr6 phases were determined by the use of first-principles calculations. The calculated heat of formation and cohesive energy indicate that Al4Sr has the strongest alloying ability as well as the highest structural stability. The elastic parameters were calculated, and then the bulk modulus, shear modulus, elastic modulus and Poisson ratio were derived. The ductility and plasticity were discussed. The results show that Al4Sr and Mg2Sr phases both are ductile, on the contrary, Mg23Sr6 is brittle, and among the three phases, Mg2Sr is a phase with the best plasticity.

关键词： magnesium alloy first-principles calculation electronic structure elastic property

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