Helium bubbles in bcc Fe and their interactions with irradiation
Helium bubbles in bcc Fe and their interactions with irradiation
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DOI：
10.1016/j.jnucmat.2014.10.027
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发表时间：
2015-07
影响因子：
3.1
通讯作者：
Xiao Gai;T. Lazauskas;Roger Smith;S. Kenny
中科院分区：
文献类型：
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作者：
Xiao Gai;T. Lazauskas;Roger Smith;S. Kenny
本文研究了体心立方铁晶格中氦泡的性质。测定了不同氦空位复合物的原子构型和形成能。0 K的结果表明，能量最有利的He与Fe的空位比从约1：1增加到约4：1的约5个空位为36个空位。小氦团簇的形成机制也被认为是。孤立的晶体和小的团簇可以迅速扩散通过晶格。随机放置的间隙He原子在500 K的MD模拟表明，在纳秒的时间尺度上的聚类与He集群包含多达4个原子在这个时间尺度上是移动的。含有4或5个原子的He团簇会喷射出Fe哑铃间隙，然后Fe哑铃间隙可以从He团簇中分离并扩散，而剩余的He-空位复合物则有效地不动。碰撞级联附近较大的气泡表明，由级联产生的Fe空位很容易成为氦空位复合物的一部分。能量障碍，他加入现有的气泡作为一个功能的氦空位比也计算。这些可以大于原始晶格中的扩散势垒，但是当气泡包含过量空位时，这些势垒较低，从而表明气泡生长可能受到动力学约束。
The properties of helium bubbles in a body-centred cubic (bcc) Fe lattice have been examined. The atomic configurations and formation energies of different He–vacancy complexes were determined. The 0 K results show that the most energetically favourable He to Fe vacancy ratio increases from about 1:1 for approximately 5 vacancies up to about 4:1 for 36 vacancies. The formation mechanisms for small He clusters have also been considered. Isolated interstitials and small clusters can diffuse quickly through the lattice. MD simulations of randomly placed interstitial He atoms at 500 K showed clustering over the time scale of nanoseconds with He clusters containing up to 4 atoms being mobile over this time scale. He clusters containing 4 or 5 atoms were shown to eject an Fe dumbbell interstitial which could then detach from the He cluster and diffuse with the remaining He–vacancy complex being effectively immobile. Collision cascades initiated near larger bubbles showed that Fe vacancies produced by the cascades readily become part of the He–vacancy complexes. Energy barriers for He to join an existing bubble as a function of the He–vacancy ratio are also calculated. These can be larger than the diffusion barrier in the pristine lattice, but are lower when the bubbles contain excess vacancies, thus indicating that bubble growth may be kinetically constrained.