单晶立方碳化硅辐照肿胀与非晶化的分子动力学模拟研究

Molecular Dynamics Simulations of Radiation-induced Swelling and Amorphization in a Single Crystal of 3C-SiC

碳化硅(SiC)材料在核能材料和半导体器件等领域有广泛的潜在应用,其辐照效应一直备受关注。结合动态恒温墙技术和恒温恒压热浴算法,本工作基于经典分子动力学模拟方法构建了单晶立方碳化硅(3C-SiC)的连续辐照模型,并研究了室温下连续几千次碰撞级联引起的SiC晶体损伤(对应的辐照剂量高达1 dpa),首次从微观上呈现了SiC从无缺陷到损伤饱和(彻底非晶化、肿胀达到极值)的完整过程。模拟发现持续辐照使得SiC密度明显降低,并储存了大量能量,其数值与文献中的实验结果比较接近。SiC非晶化过程可分为缓慢增长、快速增长、缓慢增长、完全非晶四个阶段,完全非晶的辐照剂量约为0.4 dpa,与文献中的第一性原理结果和实验结果非常接近。模拟得到的SiC肿胀与辐照剂量的关系,在0.1 dpa以下与实验结果比较接近,在0.1 dpa以上则明显偏高,这可能源自模拟与实验在剂量率上的巨大差异。这些结果表明,本文构建的计算模型比较合理,未来可用于对SiC辐照损伤微观机理的进一步研究。

Silicon carbide(SiC)materials have many important potential applications in nuclear energy systems and semiconductor materials,and their radiation effects are always of high interest among the material science community.Based on classical molecular dynamics simulations,here we combine adaptive constant-temperature wall(CTW)technique and isobaric thermostat to successfully develop a computational model for continuous irradiation damage in cubic 3 C-SiC.Using this model,we investigate the amorphization and swelling in a single crystal of 3 C-SiC under repeated particle bombardments up to 1 dpa,for the first time exhibiting the complete process of the crystal from no defects to damage saturation.It is observed that the density of SiC decrease upon continuous irradiation,with a significant amount of stored energy which is in line with the value reported in literature.We also find that the radiation-induced amorphization can be roughly separated into four stages,slow increase,fast increase,slow increase,and complete amorphization.The complete amorphization occurs at about 0.4 dpa,in line with first-principles results and experimental data in the literature.The simulated swelling as a function of dose in SiC is in good agreement with previous experimental results below 0.1 dpa,but seems too high above 0.1 dpa,which may originate from the huge difference in the dose rates of simulation and of experiments.These results indicate that our model is reasonable,and is useful for future studies on the microscopic damage mechanisms in SiC.