Chen Dong, Gao Fei, Liu Bo
Department of Physics and Electronics, Henan University, Kaifeng 475004, P. R. China.
Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
Sci Rep. 2015 Nov 12;5:16602. doi: 10.1038/srep16602.
Under the C displacement condition, we have used molecular dynamics simulation to examine the effects of grain boundaries (GBs) on the amorphization of nanocrystalline silicon carbide (nc-SiC) by point defect accumulation. The results show that the interstitials are preferentially absorbed and accumulated at GBs that provide the sinks for defect annihilation at low doses, but also driving force to initiate amorphization in the nc-SiC at higher doses. The majority of surviving defects are C interstitials, as either C-Si or C-C dumbbells. The concentration of defect clusters increases with increasing dose, and their distributions are mainly observed along the GBs. Especially these small clusters can subsequently coalesce and form amorphous domains at the GBs during the accumulation of carbon defects. A comparison between displacement amorphized nc-SiC and melt-quenched single crystal SiC shows the similar topological features. At a dose of 0.55 displacements per atom (dpa), the pair correlation function lacks long range order, demonstrating that the nc-SiC is fully amorphilized.
在C位移条件下，我们利用分子动力学模拟研究了晶界（GBs）对纳米晶硅碳化物（nc-SiC）因点缺陷积累而发生非晶化的影响。结果表明，间隙原子优先被吸收并积累在晶界处，在低剂量时晶界为缺陷湮灭提供了汇，但在高剂量时也为nc-SiC中非晶化的起始提供了驱动力。大多数存活的缺陷是间隙碳原子，以C-Si或C-C哑铃状形式存在。缺陷团簇的浓度随剂量增加而增加，其分布主要沿晶界观察到。特别是这些小团簇在碳缺陷积累过程中随后会合并并在晶界处形成非晶域。位移非晶化的nc-SiC与熔体淬火的单晶SiC之间的比较显示出相似的拓扑特征。在每原子0.55位移（dpa）的剂量下，对关联函数缺乏长程有序，表明nc-SiC已完全非晶化。
