Mechanisms underlying two kinds of surface effects on elastic constants

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	Mechanisms underlying two kinds of surface effects on elastic constants
	Tang YZ(唐溢哲); Zheng ZJ(郑志军); Xia MF(夏蒙棼); Bai YL(白以龙)
发表期刊	Acta Mechanica Solida Sinica
	2009
卷号	22 期号:6 页码:605-622
ISSN	0894-9166
摘要	ABSTRACT Recently, people are confused with two opposite variations of elastic modulus with decreasing size of nano scale sample: elastic modulus either decreases or increases with decreas- ing sample size. In this paper, based on intermolecular potentials and a one dimensional model, we provide a unified understanding of the two opposite size effects. Firstly, we analyzed the mi- crostructural variation near the surface of an fcc nanofilm based on the Lennard-Jones potential. It is found that the atomic lattice near the surface becomes looser in comparison with the bulk, indicating that atoms in the bulk are located at the balance of repulsive forces, resulting in the decrease of the elastic moduli with the decreasing thickness of the film accordingly. In addition, the decrease in moduli should be attributed to both the looser surface layer and smaller coor- dination number of surface atoms. Furthermore, it is found that both looser and tighter lattice near the surface can appear for a general pair potential and the governing mechanism should be attributed to the surplus of the nearest force to all other long range interactions in the pair po- tential. Surprisingly, the surplus can be simply expressed by a sum of the long range interactions and the sum being positive or negative determines the looser or tighter lattice near surface re- spectively. To justify this concept, we examined ZnO in terms of Buckingham potential with long range Coulomb interactions. It is found that compared to its bulk lattice, the ZnO lattice near the surface becomes tighter, indicating the atoms in the bulk located at the balance of attractive forces, owing to the long range Coulomb interaction. Correspondingly, the elastic modulus of one- dimensional ZnO chain increases with decreasing size. Finally, a kind of many-body potential for Cu was examined. In this case, the surface layer becomes tighter than the bulk and the modulus increases with deceasing size, owing to the long range repulsive pair interaction, as well as the cohesive many-body interaction caused by the electron redistribution.
收录类别	SCI
语种	英语
WOS记录号	WOS:000278405200010
关键词[WOS]	STRESS ; FILMS
WOS研究方向	Materials Science ; Mechanics
WOS类目	Materials Science, Multidisciplinary ; Mechanics
引用统计	被引频次：5[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://dspace.imech.ac.cn/handle/311007/28790
专题	非线性力学国家重点实验室
通讯作者	Tang YZ(唐溢哲)
推荐引用方式 GB/T 7714	Tang YZ,Zheng ZJ,Xia MF,et al. Mechanisms underlying two kinds of surface effects on elastic constants[J]. Acta Mechanica Solida Sinica,2009,22,6,:605-622.
APA	唐溢哲,郑志军,夏蒙棼,&白以龙.(2009).Mechanisms underlying two kinds of surface effects on elastic constants.Acta Mechanica Solida Sinica,22(6),605-622.
MLA	唐溢哲,et al."Mechanisms underlying two kinds of surface effects on elastic constants".Acta Mechanica Solida Sinica 22.6(2009):605-622.

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