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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.The diffusions of He atom and small He clusters in Ti at different temperatures are simulated by molecular dynamics. The prefactors and the activation energies of diffusion coefficients are calculated. It can be concluded that the diffusion is anisotropic. Simulations show that prefactors of diffusion coefficients are different from those of He species diffusing in different directions, but the activation energies are the same. The result demonstrates that it is insufficient to predict the diffusion behavior of He in metal when only the energy barrier in static lattice is considered. Dynamics calculations are necessary to obtain the correct prefactors. Another counterintuitive observation is that He-dimer migrates more quickly than single He atom does at room temperature. The results emphasize the importance of dynamics simulations in predicting diffusion behavior of He in metals.
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Keywords:
- molecular dynamics /
- diffusion coefficient /
- anisotropy /
- helium
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[28] Cleri F, Rosato V 1993 Phys. Rev. B 48 22
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[39] -
[1] Wilson W D, Bisson C L, Baskes M I 1981 Phys. Rev. B 24 5616
[2] [3] Wilson W D 1982 Radiat. Effec. 78 11
[4] Wang P X, Song J S 2002 The Permeation of Helium and Tritium in Materials (Beijing: National Defence Industry Press) p6 (in Chinese) [王佩璇、宋家树 2002 材料中的氦及氚渗透 (北京: 国防工业出版社) 第6页 ]
[5] [6] [7] Pu J, Yang L, Zu X T, Gao F 2007 Physica B 398 65
[8] Ao B, Wang X, Hu W, Yang J 2008 Phys. Stat. Sol. B 245 1493
[9] [10] Zhang C H, Chen K Q, Wang Y S, Sun J G 1997 Acta Phys. Sin. 46 1774 (in Chinese) [张崇宏、陈克勤、王引书、孙继光 1997 物理学报 46 1774]
[11] [12] [13] Adams J B, Wolfer W G 1988 J. Nucl. Mater. 158 25
[14] [15] Boisvert G, Lewis L J 1996 Phys. Rev. B 54 2880
[16] Xia J X, Hu W Y, Yang T Y, Ao B Y, Wang X L 2006 Phys. Stat. Sol. B 243 579
[17] [18] Finnis M W, Agnew P, Foreman A J E 1991 Phys. Rev. B 44 567
[19] [20] Hou Q, Hou M, Bardotti L, Prvel B, Mlinon P, Perez A 2000 Phys. Rev. B 62 2825
[21] [22] [23] Allen M P, Tildesley D J 1987 Computer Simulation of Liquids (New York: Oxford University Press)
[24] [25] Baskes M I, Stan M 2003 Metallurg. Mater. Trans. A 34 435
[26] [27] Horstemeyer M F, Baskes M I 2000 Mater. Res. Soc. Symp. Proc. 578 15
[28] Cleri F, Rosato V 1993 Phys. Rev. B 48 22
[29] [30] [31] Chen M, Hou Q, Wang J, Sun T, Long X, Luo S 2008 Solid State Commun. 148 178
[32] [33] Chen M, Wang J, Hou Q 2009 Acta Phys. Sin. 58 1149 (in Chinese) [陈 敏、汪 俊、侯 氢 2009 物理学报 58 1149]
[34] [35] Chen M, Hou Q 2010 Acta Phys. Sin. 59 1185 (in Chinese) [陈 敏、侯 氢 2010 物理学报 59 1185]
[36] Chen M, Hou Q 2010 Nucl. Sci. Techn. 21 257
[37] [38] Zinke-Allmang M, Feldman L C, Grabow M H 1992 Surf. Sci. Rep. 16 377
[39]
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