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银纳米晶能量与微观结构演变的分子动力学模拟

发布时间:2019-01-12 10:03
【摘要】:近年来,纳米材料的应用越来越广泛,特别是对贵金属纳米材料的研究更是纳米材料领域的研究热点之一。本文采用分子动力学方法和嵌入原子势,对不同尺寸银纳米晶在高温弛豫下的能量和微观结构演变进行了模拟研究。首先,对于沿相互垂直{110}、{211}和{111}面切割形成的近正方体截面银纳米晶,体系温度、体系尺寸均对原子的能量分布有影响:同种体系原子平均势能随温度的升高而增加,而在相同温度下的不同体系原子能量分布密度比较相近,但是体系尺寸越小,原子平均能量越高,原子势能在高能区所占的比例越多,能量越分散。通过模拟还发现,体系在升温过程中,原子平均能量随温度的升高出现线性增加,当温度到达某一温度(熔点)时体系会出现能量的突变,这个突变点大小与体系尺寸有关,尺寸越小,突变温度越低。然后,体系能量的改变使原子的排列发生改变,银纳米晶随着温度的上升,从规则的立方体结构开始,先从角再到边再到面出现原子迁移重组,最后银纳米晶演变为球形。银纳米晶的熔化演变过程表明:纳米晶的高温熔化可分三个阶段,即很短时间的表面预熔,较长时间的表面原子无序和重排,迅速的全面熔化。最先出现原子迁移重组的是八个顶角,其次是十二条棱边,最后是六个面,这种迁移重组使得纳米晶的比表面减小,体系的能量减小。另外,银纳米晶在熔化过程中出现明显的各向异性行为:)211(面热稳定性最低,最先熔化,其次是(110)面,热稳定性最高的是?111?面,最后熔化。研究结果还表明:不同晶面最层和次外层的稳定寿命相差不大且时间极短,第三层及以内的稳定寿命较长且依次少量增加。但对于不同晶面,第三层及以内的稳定寿命差异较大,最短的是)211(面,最长的是?111?面,(110)面介于两者之间。
[Abstract]:In recent years, the application of nanomaterials has become more and more extensive, especially the research of noble metal nanomaterials is one of the research hotspots in the field of nanomaterials. In this paper, the energy and microstructure evolution of silver nanocrystals with different sizes under high temperature relaxation have been simulated by molecular dynamics method and intercalated atomic potential. First, the temperature of the silver nanocrystals with near-square cross-section, which are cut along the faces of {110}, {211} and {111}, is calculated. The size of the system has an effect on the energy distribution of atoms: the average potential energy of the same system increases with the increase of temperature, but the energy distribution density of different systems at the same temperature is similar, but the smaller the system size is, The higher the average atomic energy is, the more the potential energy in the high energy region is, and the more dispersed the energy is. It is also found by simulation that the average atomic energy increases linearly with the increase of temperature during the heating process. When the temperature reaches a certain temperature (melting point), there will be a sudden change of energy in the system, which is related to the size of the system. The smaller the size, the lower the mutation temperature. Then, the change of energy of the system changes the arrangement of atoms. With the increase of temperature, the silver nanocrystals begin with the regular cube structure, and the atoms migrate and recombine from angle to edge to surface, finally silver nanocrystals become spherical. The melting evolution of silver nanocrystals shows that the melting of nanocrystals at high temperature can be divided into three stages: surface premelting for a very short time, disordered and rearranged surface atoms for a long time, and rapid total melting. The atom migration recombination occurs first in eight vertices, then in 12 edges, and finally in six surfaces. This migration recombination reduces the specific surface of nanocrystals and reduces the energy of the system. In addition, the anisotropic behavior of silver nanocrystals in the melting process is obvious:) 211 (surface thermal stability is the lowest, first melting, followed by (110) surface, the highest thermal stability is? 111? Face, finally melt. The results also show that the stable life of the most layer and the subouter layer of the different crystal planes is not different and the time is very short, and the stable life of the third layer and the inner layer is longer and slightly increased in turn. But for different crystal planes, the stability life of the third layer and the inner layer varies greatly, the shortest one is 211 (face, the longest is? 111? The (110) plane is between the two.
【学位授予单位】:江西理工大学
【学位级别】:硕士
【学位授予年份】:2015
【分类号】:TB383.1;O614.122

【参考文献】

相关期刊论文 前3条

1 陈远铭;罗有萍;么小江;;<111>轴铜纳米线能量分布特征的原子模拟研究[J];赣南师范学院学报;2008年06期

2 曾杰;夏晓虎;张强;王q,

本文编号:2407654


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