Thermal stability of helium-vacancy clusters in iron
Thermal stability of helium-vacancy clusters in iron
复制标题
DOI：
10.1016/s0168-583x(02)01832-3
复制
发表时间：
2003-04-01
影响因子：
1.3
通讯作者：
de la Rubia, TD
中科院分区：
文献类型：
--
作者：
Morishita, K;Sugano, R;de la Rubia, TD
用Ackland Finnis-Sclair势、Wilson-Johnson势和Ziegler-Biersack-Littmark-Beck势分别描述了Fe-Fe、Fe-He和He-He之间的相互作用，用分子动力学方法计算了Fe中氦空位团簇的热稳定性。计算得到的团簇中氦原子个数n和空位个数m都在0~20之间。根据计算的团簇形成能，得到了间隙氦原子、孤立空位和自间隙铁原子与氦-空位团簇的结合能。所有的结合能都不太依赖于团簇的大小，但它们主要取决于团簇的氦/空位比(n/m)。空位与氦-空位团簇的结合能随这一比例的增加而增加，表明氦通过显著减少热空位发射而延长了团簇寿命。另一方面，氦原子和铁原子与氦空位原子团簇的结合能均随氦空位比的增加而降低，这表明氦空位比较高的原子团簇可能发生自间隙原子(SiAs)的热发射(即Frenkel对的产生)和热氦发射。团簇的热稳定性取决于团簇的氦空位比，决定于空位、SiAs和氦的热发射之间的竞争过程。计算的团簇热稳定性与氦注入后退火过程中氦从α-Fe中脱附的实验观测结果相一致。(C)2002 Elsevier Science B.V.保留所有权利。
Molecular dynamics calculations were performed to evaluate the thermal stability of helium vacancy clusters (HenVm) in Fe using the Ackland Finnis-Sinclair potential, the Wilson-Johnson potential and the Ziegler-Biersack-Littmark-Beck potential for describing the interactions of Fe-Fe, Fe-He and He-He, respectively. Both the calculated numbers of helium atoms, n, and vacancies, m, in clusters ranged from 0 to 20. The binding energies of an interstitial helium atom, an isolated vacancy and a self-interstitial iron atom to a helium-vacancy cluster were obtained from the calculated formation energies of clusters. All the binding energies do not depend much on cluster size, but they primarily depend on the helium-to-vacancy ratio (n/m) of clusters. The binding energy of a vacancy to a helium-vacancy cluster increases with the ratio, showing that helium increases cluster lifetime by dramatically reducing thermal vacancy emission. On the other hand, both the binding energies of a helium atom and an iron atom to a helium-vacancy cluster decrease with increasing the ratio, indicating that thermal emission of self-interstitial atoms (SIAs) (i.e. Frenkel-pair production), as well as thermal helium emission, may take place from the cluster of higher helium-to-vacancy ratios. The thermal stability of clusters is decided by the competitive processes among thermal emission of vacancies, SIAs and helium, depending on the helium-to-vacancy ratio of clusters. The calculated thermal stability of clusters is consistent with the experimental observations of thermal helium desorption from alpha-Fe during post-He-implantation annealing. (C) 2002 Elsevier Science B.V. All rights reserved.