De Backer A, Domain C, Becquart C S, Luneville L, Simeone D, Sand A E, Nordlund K
CCFE-Culham Centre for Fusion Energy, Abingdon, Oxon OX14 3DB, United Kingdom.
J Phys Condens Matter. 2018 Oct 10;30(40):405701. doi: 10.1088/1361-648X/aadb4e. Epub 2018 Aug 20.
The impacts of ions and neutrons in metals cause cascades of atomic collisions that expand and shrink, leaving microstructure defect debris, i.e. interstitial or vacancy clusters or loops of different sizes. In De Backer et al (2016 Europhys. Lett. 115 26001), we described a method to detect the first morphological transition, i.e. the cascade fragmentation in subcascades, and a model of primary damage combining the binary collision approximation and molecular dynamics (MD). In this paper including W, Fe, Be, Zr and 20 other metals, we demonstrate that the fragmentation energy increases with the atomic number and decreases with the atomic density following a unique power law. Above the fragmentation energy, the cascade morphology can be characterized by the cross pair correlation functions of the multitype point pattern formed by the subcascades. We derive the numbers of pairs of subcascades and observed that they follow broken power laws. The energy where the power law breaks indicates the second morphological transition when cascades are formed by branches decorated by chaplets of small subcascades. The subcascade interaction is introduced in our model of primary damage by adding pairwise terms. Using statistics obtained on hundreds of MD cascades in Fe, we demonstrate that the interaction of subcascades increases the proportion of large clusters in the damage created by high energy cascades. Finally, we predict the primary damage of 500 keV Fe ion in Fe and obtain cluster size distributions when large statistics of MD cascades are not feasible.
金属中离子和中子的撞击会引发一系列原子碰撞，这些碰撞会不断扩展和收缩，留下微观结构缺陷碎片，即不同尺寸的间隙或空位团簇或环。在德贝克尔等人（2016年，《欧洲物理快报》115卷，26001期）的研究中，我们描述了一种检测首次形态转变（即级联分裂为子级联）的方法，以及一种结合二元碰撞近似和分子动力学（MD）的初级损伤模型。在本文中，我们研究了包括钨、铁、铍、锆以及其他20种金属在内的情况，证明了分裂能量随原子序数增加而增加，随原子密度降低而降低，遵循独特的幂律。在分裂能量之上，级联形态可以通过子级联形成的多类型点模式的交叉对关联函数来表征。我们推导了子级联对的数量，并观察到它们遵循断裂幂律。幂律断裂处的能量表明当级联由小子级联的链节装饰的分支形成时的第二次形态转变。通过添加成对项，我们在初级损伤模型中引入了子级联相互作用。利用在铁中数百个MD级联获得的统计数据，我们证明子级联相互作用增加了高能级联造成的损伤中大型团簇的比例。最后，我们预测了500 keV铁离子在铁中的初级损伤，并在无法获得大量MD级联统计数据时获得了团簇尺寸分布。
