首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 140 毫秒
1.
张明  于文  张君  张远仪  王文魁 《物理学报》1996,45(10):1724-1728
利用原位X射线衍射技术得到非晶调制多层膜Nb/Si中的互扩散系数与退火温度的关系,调制周期L=3.2nm的非晶调制多层膜是用粒子溅射方法制备的.温度范围为423—523K的有效互扩散系数通过原位测量多层膜的一级调制峰强度与退火温度之间的关系而得到.利用缺陷陷阱延迟扩散机制解释了所得到的扩散系数与退火温度的关系.建立了可以解释较小前置系数的模型 关键词:  相似文献   

2.
陈敏 《物理学报》2011,60(12):126602-126602
采用分子动力学方法模拟了不同温度下He原子及He团簇在金属Ti中的迁移特性,并计算了扩散前系数和激活能. 研究发现这种扩散的各向异性非常显著,具体表现在He原子及He团簇在不同方向上扩散系数的前系数完全不同,但它们的激活能却相同. 研究表明:在预测金属中He的扩散行为时,必须采用动态模拟方法才能得到准确的前系数,仅仅考虑势垒的静态模拟方法是不行的. 另外,还发现一个不同于直觉的现象,即较低温度下He二聚物的扩散系数比单个He原子的扩散系数大;此外,在所模拟的温度范围内Arrhenius方程能够很好地描述它们的扩散. 这说明动力学模拟对预测金属中He的扩散行为具有重要的意义. 关键词: 分子动力学 扩散系数 各向异性 氦  相似文献   

3.
Ni在非晶Si中扩散机制的原位X射线衍射研究   总被引:1,自引:0,他引:1       下载免费PDF全文
汪卫华  白海洋  陈红  张云  王文魁 《物理学报》1993,42(9):1505-1509
通过对非晶Ni和Si多层组分调制膜(ML)中Ni和Si互扩散规律的原位X射线衍射法研究,考察了金属Ni在非晶Si(a-Si)中的扩散现象。得到了较低温度下Ni在非晶Si中扩散系数及规律,并且提出了Ni在a-Si中受非平衡缺陷延迟的间隙扩散机制。这个扩散模型较好地解释了Ni在a-Si中的扩散。 关键词:  相似文献   

4.
为了探索气体在固体表面高分子链中的扩散,使用分子动力学(MD)的方法,对H2,D2,T2在聚苯乙烯与金属铜(PS-Cu)界面的扩散进行了计算模拟,通过所得到气体的均方位移计算了气体在不同金属表面与聚苯乙烯界面中的扩散系数。结果显示:气体在界面的扩散系数比在聚苯乙烯本体中的扩散系数小,气体在PS-Cu(110)界面的扩散系数最大,在PS-Cu(111)界面的扩散系数最小。计算和分析了PS与金属表面的相互作用,发现其相互作用能越大,气体在此界面的扩散系数越小。同时,金属表面的晶面密度对气体在界面中的扩散也有一定的影响。  相似文献   

5.
挥发性有机化合物(VOCs)对人体健康非常有害,已引起越来越多的室内空气质量研究人员的重视。本文利用分子动力学模拟方法研究了常见VOCs在聚氯乙烯板中的扩散,基于聚类分析法计算了扩散系数,研究了不同温度、不同密度的影响。结果表明:相同温度下,扩散系数苯DEHP甲醛,有机分子在PVC中的扩散系数随PVC密度的增加而减小,上述结果从微观层面加深了对VOCs在建筑材料中扩散过程的理解和认识,对于室内空气环境净化领域的研究和产品开发具有参考价值。  相似文献   

6.
研究了偏压控制下的粒子在破缺媒介中的扩散动力学.基于平均首次通过时间理论导出了粒子在偏压破缺势场中的有效扩散系数的近似表达式.结果显示粒子的有效扩散系数被显著地增大,用粒子概率密度分布函数的波包展宽对此机制给出了解释.进一步,本文提出有效动力学温度和有效阻尼相结合的概念,对爱因斯坦扩散关系进行了推广.  相似文献   

7.
实验测量罗丹明B在大肠杆菌悬浮液中的扩散系数,考察大肠杆菌悬浮液温度、浓度和细菌活性对罗丹明B扩散传质的影响。实验结果表明,罗丹明B在悬浮液中的有效扩散系数比其在磷酸缓冲盐溶液(PBS)中的扩散系数大1个数量级,且有效扩散系数随悬浮液温度升高和细菌浓度增大而增大;细菌自驱动行为是强化悬浮液中小分子扩散传质的重要因素,罗丹明B的活性扩散系数随细菌悬浮液浓度增加和温度升高而增大,活性扩散系数因细菌的集群运动会随悬浮液浓度变化发生阶跃增大;均方位移和扩散时间的对应关系表明罗丹明B的扩散在短时间内为标准菲克扩散,一段时间后转变为超扩散,且转变时间随悬浮液温度升高而延迟,随着悬浮液浓度增加而提前。  相似文献   

8.
Cd0.9Zn0.1Te晶体的Cd气氛扩散热处理研究   总被引:1,自引:0,他引:1       下载免费PDF全文
将生长得到的Cd0.9Zn0.1Te晶体在Cd气氛下及不同的温度条件下进行了退火处理. 借助已建立的退火处理过程中Cd1-xZnxTe晶体材料电阻率及导电类型变化和扩散杂质的扩散系数之间关系的模型,结合实验数据,获得了1073 K,973 K和873 K下Cd在Cd0.9Zn0.1Te晶体中的扩散系数,并估算了其激活能. 通过使用获得的扩散系数,研究了在不同温度及饱和Cd气氛下,退火时间对Cd0.9Zn0.1Te晶体电阻率分布及导电类型等的变化的影响.  相似文献   

9.
应用核磁共振成像(MRI)技术可视化研究CO2在癸烷中的扩散,在MRI系统采集图像的同时,应用双室压力衰减法(PVT法)监测压力,通过对MRI图像进行信号强度分析,可得到CO2的无量纲浓度分布,然后基于菲克定律应用有限体积法可计算得出与扩散距离和扩散时间有关的扩散系数,并可得到任意扩散时间范围内的整体平均扩散系数,MRI方法得出的扩散平衡时间范围内的整体平均扩散系数与PVT法相比较误差为2.7%,并且与相似条件下的前人实验结论具有相同的数量级(10–9).根据实验结果得出,扩散系数沿扩散方向下降且随时间以指数形式降低,整体平均扩散系数随扩散时间的增加而减小.  相似文献   

10.
利用低相干动态光散射方法研究了悬浮液中布朗运动颗粒的扩散特性。利用单散射理论,考虑悬浮液的折射率随分数的变化,通过解析检测到的单散射光的光谱得到不同分数悬浮液中颗粒的有效扩散系数。讨论了三种不同粒径颗粒的有效扩散系数随悬浮液体积分数的变化关系。结果表明,浓悬浮液中布朗运动颗粒的扩散特性受到静态结构因子及颗粒间流体动力学相互作用的影响,随体积分数的增加而减小。在0.01~0.2的体积分数范围内,有效扩散系数测量值与采用Percus-Yevick近似和Cohen-de Schepper近似得到的理论值吻合较好。证明了低相干动态光散射法可用来研究不同体积分数的悬浮液中颗粒的扩散特性。  相似文献   

11.
The mobility of self-interstitials in α-zirconium (α-Zr) is studied with molecular dynamic (MD) and molecular static (MS) simulations, using Ackland’s many-body inter-atomic potential. The basal crowdion configuration is found to be the ground state. Four types of diffusion jumps can be identified via MS, in-plane in-line, in-plane off-line, out-of-plane in-line and out-of-plane off-line. The in-plane migration is dominated by one-dimensional crowdion motion along the [110] directions, interrupted from time to time by off-line or out-of-plane jumps. Based on the MS results, the activation energies and pre-exponentials for the diffusion processes are determined by fits to the Arrhenius plots of Dc and Da. The diffusional anisotropy factor Dc/Da is also obtained, and compares well with experimental results. The mean frequency of each type of jumps is then found using Monte Carlo simulation, and is reported as a function of temperature. The mean lifetime and mean free path of the one-dimensional mobility are then obtained. The 1-D mean free path is found to be unimportant for sink separations involved under the usual irradiation damage conditions. Received: 4 March 2002 / Accepted: 4 April 2002 / Published online: 10 September 2002 RID="*" ID="*"Corresponding author. E-mail: Chung.Woo@polyu.edu.hk  相似文献   

12.
13.
S. Barzilai  N. Argaman  D. Fuks 《Surface science》2009,603(13):2096-2101
CaF2 is a thermodynamically stable, non-reactive compound, displaying a relatively high contact angle with pure liquid metals. A remarkable decrease of this contact angle takes place when small amounts of Ti are added to liquid In, while a relatively small change of the contact angle is observed when it was added to liquid Sn. In order to understand the reason for this different behavior, ab-initio calculations were carried out in the framework of Density Functional Theory. The effect of the In-Ti and Sn-Ti inter-atomic interactions in the vicinity of CaF2(1 1 1) slab is discussed using the results of modest calculations for several Me-Ti configurations on CaF2(1 1 1) slabs. The results of the calculations indicate that the level of the interaction between the Me and the Ti atom affects the (Me-Ti)/CaF2 interface composition, the interfacial energy and the wetting behavior.For the system with stronger inter-atomic attraction in the melt (Sn-Ti alloys), Ti atoms prefer to be surrounded by Sn atoms, and only weakly affect the metal/substrate interfacial energy and, thus the observed contact angle. However, for weak inter-atomic attraction (In-Ti alloys) an enhanced Ti adsorption at the metal/substrate interface takes place and leads to decrease the interfacial energy and improved wetting. The differences in the wetting behavior for these systems are discussed in terms of the total energy of each system, the electron charge re-distribution and the electron Density of States.  相似文献   

14.
The angular distribution of 2.8 MeV helium ions backscattered from silicon crystals containing self-interstitials has been calculated by channeling computer simulations for a double alignment channeling configuration. The structures of the self-interstitial defects are assumed to be the split <110> interstitial and the split <100> di-interstitial with various inter-atomic distances. The obtained profiles of the backscattering yield are found to show shapes characteristic for each structure which can be used for differentiating between these structures. When comparing these profiles with experimental profiles obtained with the same double alignment channeling configuration in a previous study one finds reasonable agreement for the split <110> interstitial defect with an inter-atomic distance of 1.76 Å.  相似文献   

15.
Generation of X-ray standing waves in a multi-trilayer system with a varying periodicity along its depth is described. Microstructures of a synthetic 15-period Pt/Ni/C multilayer, which has such a varying periodicity, are investigated using X-ray reflectivity (XRR) and X-ray standing wave (XSW) analysis. Microstructural parameters, e.g., thicknesses and electron densities of individual layers, interface roughnesses, varying periodicity along the depth, etc. are precisely determined by the XRR technique. The variation of period is essentially introduced in multilayer fabrication by varying the thickness of the C-layer as a function of depth. The linear increase in C-layer thickness from the bottom of the multilayer towards the surface of the multilayer structure is found by simulating the XRR data with a depth-graded multilayer model. Intensity of the XSW field is computed as a function of depth over the first order Bragg peak. Integrated intensities over the Pt- and the Ni-layers are computed and compared with the measured fluorescence yield from Pt and Ni. Sensitivity for the detection of inter-atomic diffusion across the interfaces in comparison to multi-bilayer systems, such as Pt/C multilayer, is discussed.  相似文献   

16.
陈海军  薛具奎 《物理学报》2008,57(7):3962-3968
研究了平面Bessel型光晶格(BL)中双组分玻色-爱因斯坦凝聚(BECs)体系的基态解.从描述三维(3D)BECs体系的动力学方程Gross-Pitaevskii方程(GPE)出发,当垂直方向囚禁频率远大于平面上囚禁频率时,得到了描述2D-BECs体系的动力学方程.利用双组分BECs体系中原子之间相互作用与BL强度相互平衡的条件,得到了平面BL光晶格中2D-GPE的一组基态精确解,给出了基态的原子数分布,总原子数和能量与原子之间相互作用强度及BL势的关系.相对于单组分BEC体系,由于不同组分原子相互作用的存在,使得BL光晶格中双组分BECs基态具有更丰富的结构.当不存在不同组分原子之间的相互作用时,模型简化到单组分体系,并给出了相应的基态解,原子数分布和能量. 关键词: Bessel型光晶格 基态解 双组分玻色-爱因斯坦凝聚  相似文献   

17.
The ground-state configurations and spectrum of two parallel two-dimensional classical atoms are obtained as a function of the inter-atomic distance ( ). The classical particles are confined by parabolic potentials and repel each other through a Coulomb potential. As a function of we find several configurational transitions which are of first or second order. For first- (second-) order transitions the first (second) derivative of the energy with respect to is discontinuous, the radial position of the particles changes discontinuously (continuously) and the frequency of the eigenmodes exhibit a jump (softening of a mode). In the limit of an infinite number of electrons the Wigner bilayer system is recovered which moves through five different stable crystalline phases as a function of . For unequal strength of parabolic confinement we find that the number of configurational transitions increases.  相似文献   

18.
金属熔体黏度与结构相关性的分子动力学模拟   总被引:2,自引:0,他引:2       下载免费PDF全文
运用EAM(embed atom method)作用势,采用非平衡分子动力学模拟获得Al熔体的偶分布函数与黏度数值随温度的变化曲线,偶分布函数的计算结果与实验值符合得较好.对模拟所得到的黏度数据编程实现黏度的Arrhenius公式拟合,得到激活能E.并利用模拟所得到的黏度值及激活能对Lennard-Jones(L-J)作用势进行修正,获得黏度与偶分布函数及原子间相互作用势之间的关系式,两条黏度拟合曲线与分子动力模拟结果符合得比较好,说明拟合程序的编写是比较成功的,实现了对L-J作用势的修正.该研究为金属及合金原子间相互作用势的建立提供了新的思路. 关键词: 非平衡分子动力学模拟 L-J作用势修正 Al熔体 结构与黏度相关性  相似文献   

19.
晶体中隐含的半群结构   总被引:1,自引:0,他引:1  
陈难先 《物理》2006,35(5):359-361
序列性和莫比吾思反演已应用到物理中各类逆问题,诸如黑体辐射逆问题、比热逆问题和各类费米体系逆问题.文章要介绍这种方法对提取体材料中原子相互作用势的结合能逆问题的应用,以及对提取界面两侧原子间相互作用势的界面粘结能逆问题的应用.这些方法的关键是要发现对象体系中的半群结构.  相似文献   

20.
We study ground-state properties of interacting two-component boson gases in a one-dimensional harmonic trap by using the exact numerical diagonalization method. Based on numerical solutions of many-body Hamiltonians, we calculate the ground-state density distributions in the whole interaction regime for different atomic number ratio, intra- and inter-atomic interactions. For the case with equal intra- and inter-atomic interactions, our results clearly display the evolution of density distributions from a Bose condensate distribution to a Fermi-like distribution with the increase of the repulsive interaction. Particularly, we compare our result in the strong interaction regime to the exact result in the infinitely repulsive limit which can be obtained by a generalized Bose-Fermi mapping. We also discuss the general case with different intra- and inter-atomic interactions and show the rich configurations of the density profiles.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号