Interatomic many-body potential model in metal

在本文中,我们构造了金属Ta元素的Finnis-Sinclair型的嵌入原子势。并采用蒙特卡罗方法求解给出了此元素的多体势函数的参数。结果显示,本文拟合的参数能够较好的反映这种元素的结构特征和物理性质。福建省自然科学基金(批准号:Z0513004)资助的课

Testing System of Phosphor Excited by Blue LED Based on Integral Sphere

为尽可能反映荧光粉在实际工作条件下的发光性质,准确测量荧光粉的发光性能,提出了一种基于积分球的荧光粉发光性能测试系统。该系统采用蓝光lEd作为激发光源,配置有TEC控温系统对光源有效实施控温,可提供持续稳定的激发荧光粉发光。采用出光筒控制光源方向和积分球收集光线,能有效防止能量损失,提高测试的精确性。通过实验得到了不同强度蓝光激发下的荧光粉光谱功率分布以及发光效能、量子效率、光转换效率等参数的变化规律。随着驱动电流的增大,由于蓝光芯片内量子限制斯塔克效应,从而导致蓝光峰值波长出现小幅度的蓝移。三种效率在小电流下基本呈线性下降趋势,且在大电流下趋于平缓。实验结果表明,该系统及方法可以有效地评价实际lEd芯片工作状态下的荧光粉发光性能。A testing system for phosphor luminous characteristics based on integral sphere is proposed so as to show luminous characteristics of phosphor at actual operation circumstances and measure its luminous characteristics accurately.Blue LED is used as an excited source in the system.TEC temperature control system is used to control the temperature of the source effectively.And continuous and stable excited light is provided to excite phosphor illumining.Energy loss is prevented effectively and testing accuracy is enhanced for the direction of source controlled by a light tube and light ray collected by integral sphere.Based on experiments,spectrum power distributions of phosphor excited by blue light with difference light strength and variation rules of parameters such as luminous efficiency,quantum efficiency and light conversion efficiency are got.With the increasing of driving current,a small blue shift appears in blue light peak wavelength for quantum confined Stark effect in blue light chip.Three kinds of efficiency almost show linear decline trend at low current and then approach to constant at high current.Experimental results show that luminous characteristics of phosphor on real LED chip at operation state can be evaluated effectively by the system and method.国家自然科学基金项目(11104230); 福建省重点科技项目(2011H6025;2012H0039

The elastic properties and energy characteristics of Au nanowires: an atomistic simulation study

This paper have performed molecular static calculations with the quantum corrected Sutten-Chen type many body potential to study size effects on the elastic modulus of Au nanowires with [100], [110] and [111] crystallographic directions, and to explore the preferential growth orientation of Au nanowires. The main focus of this work is the size effects on their surface characteristics. Using the common neighbour analysis, this paper deduces that surface region approximately consists of two layer atoms. Further, it extracts the elastic modulus of surface, and calculate surface energy of nanowire. The results show that for all three directions the Young's modulus of nanowire increases as the diameter increases. Similar trend has been observed for the Young's modulus of surface. However, the atomic average potential energy of nanowire shows an opposite change. Both the potential and surface energy of [110] nanowire are the lowest among all three orientational nanowires, which helps to explain why Au nanowires possess a [110] preferred orientation during the experimental growth proceeds

Structural Stabilities of Ordered Arrays of Nb-4 Clusters on NaCl(100) Surface

National Natural Science Foundation of China [10774124]Adsorption of ordered (2 x 2) arrays of Nb-4 clusters on the insulating surface of NaCl(100) is studied by the first-principles calculations within the density functional theory. The calculations on the relaxed geometries and cohesive energies show that both the tetrahedron and quadrangle-Nb-4 can be stably adsorbed on this substrate, which may have important applications. The adsorption of quadrangle-Nb-4 on the NaCl(100) surface is more stable than that of tetrahedron-Nb-4. Both the Nb-4 clusters studied and a single Nb atom prefer the top site of the Cl atom in the NaCl(100) surface. Electronic structure analysis suggests that the interactions between the Nb-4 clusters and the substrate are weak

Single-crystalline and multiple-twinned gold nanoparticles: an atomistic perspective on structural and thermal stabilities

National Natural Science Foundation of China [51271156, 11204252]; Natural Science Foundation of Fujian Province of China [2013J06002]; Fundamental Research Funds for the Central Universities of China [2012121010]Morphologies of gold nanoparticles play an important role in determining their chemical and physical (catalytic, electronic, optical, etc.) properties. Therefore, a fundamental understanding of the morphological stability is of crucial importance to their applications. In this article, we employed atomistic simulations to systematically investigate the structural and thermal stabilities of gold particles with eight representative nanoshapes, including single-crystalline and multiple-twinned structures. Our investigation has revealed that the truncated octahedron and the octahedron possessed the best structural stability, while the tetrahedron and the icosahedron did the worst. Further analyses have discovered different thermal stabilities and diverse melting behaviors in these particles. Especially, an inhomogeneous melting of the icosahedron was disclosed, and the relevant mechanism was elucidated. This study provides significant insight not only into the experimental preparation of gold nanoparticles but also into the design of gold nanostructures with both high catalytic activity and excellent stability

纪念五四宪法颁布暨全国人民代表大会成立五十周年理论研讨会纪要

今年 9月是五四宪法颁布、全国人民代表大会成立五十周年。五四宪法是新中国的第一部宪法 ,为我国的社会主义民主法制奠定了基础 ,具有划时代的意义。坚持和完善人民代表大会制度 ,是新的历史条件下推进政治体制改革和社会主义政治文明建设的重要内容。基于“以学术表达纪念、以纪念促进学术”的目的 ,中国社会科学院法学研究所于 2 0 0 4年 9月 5日举办了“纪念五四宪法颁布暨全国人民代表大会成立五十周年理论研讨会”。来自全国各地的 70余位代表莅临会议 ,研讨了诸多热点和前沿问题

The nonlinear elastic behavior of crystalline solids:An atomistic simulation study

采用分子静力学结合量子修正Sutten-Chen型多体势研究了Ni单晶体在受单向拉伸和压缩载荷作用下的弹性响应.考虑了三种加载方式,即[001],[011]和[111]单向加载.模拟的结果表明:晶体在[011]单向加载下的弹性变形表现出强烈的非线性效应,然而沿[001]和[111]单向加载时,它的横向变形表现为各向同性.进一步讨论了杨氏模量和泊松比与应变的关系,并和第一性原理计算的结果做了比较.In this paper,we employ molecular static approach with quantum corrected Sutten-Chen many-body potential to study the elastic responses of nickel monocrystal subjected to uniaxial tensile and compressive loading,and consider three different loadings,i.e.,the [001],[011] and [111] loding.The simulated results show that strong nonlinear effects are found in the elastic behavior of monocrystal under the [011] loading,while the lateral deformations are essentially isotropic under [100] and [111] loadings.The further discussions are focused on the dependence of the Young's moduli and Poisson's ratios on the applied strain,and a brief comparison with first-principles calculations is also presented.国家自然科学基金(批准号:10702056);; 兰州理工大学甘肃省有色金属新材料国家重点实验室资助的课题~

Magnetism of Small-sized Al_n Clusters(n=2～7)

使用自旋极化的密度泛函理论下的第一原理方法,对简单金属铝的小团簇Aln(n=2～7)的结构特性和磁性进行了理论计算.结果表明:团簇的结合能随着团簇中原子数的增加而增大;虽然Al是简单金属,但是其小团簇Aln(n=2～7)具有磁性,磁矩在1μB和2μB间变化;通过能级图分析了Aln团簇磁矩的变化规律.此外,还分析了Aln团簇的磁矩、结合能、能量的一阶和二阶差分随原子数n的变化,讨论了最稳定团簇Al5的电子结构和电荷密度.The structural properties and magnetism of Aln small clusters(n=2~7) were studied by employing the first-principles calculations based on the spin-polarized density functional theory.The calculation results showed that:the binding energies increased with the number of atoms in the Alnclusters,although Al was a simple metal,the small-sized Aln clusters(n=2~7) could exhibit magnetism,with the magnetic moments changing between 1 μB and 2 μB.From the plot of energy levels,the magnetic moments of spin-polarized Aln clusters were discussed.Furthermore,the magnetic moment,the binding energy,the first and second differences of binding energies versus the number of atoms in the clusters were analyzed.The electronic structure and charge density of the most stable cluster Al5 were also discussed.国家自然科学基金(10774124,10702056)资

The deformation mechanism of nanofilm with void under tensile loading:An atomistic simulation study

采用分子静力学方法结合量子修正的Sutton-Chen多体势研究了含圆孔的纳米薄膜在单向加载过程中的力学行为,并采用共近邻分析方法研究了薄膜的微结构演化过程.模拟结果表明:孔洞的引入显著地降低了纳米薄膜的杨氏模量和屈服应力;在拉伸过程中,孔洞的形状随着应变的增加逐渐由圆形变为椭圆形,最终孔洞闭合;纳米薄膜在进入塑性变形阶段后,薄膜内部出现原子的堆跺层错,这种层错结构的出现是肖克莱不全位错在薄膜内部沿着{111}面的[112]方向运动的结果.In this paper,we employ molecular static approach with quantum corrected Sutten-Chen many-body potential to study the mechanical behavior of nickel nanofilm during uniaxial loading,and investigate its microstructure by common neighbor analysis methods.The simulated results show that the existence of void significantly weakens the Young's modulus and yield stress of nanofilm;with the increased strain,the shape of void changes from circular into elliptical,and the void is eventually entirely closed.The plastic deformation of nanofilm is characterized by {111} glide associated with Shockley partial dislocations,resulting in the formation of stacking faults.国家自然科学基金(批准号:10702056,10774124);; 福建省高等学校新世纪优秀人才支持计划资助的课题~