钨中自间隙原子团簇扩散行为的分子动力学模拟

钨被视为未来聚变堆中最有可能全面使用的面对等离子体材料。而在未来聚变堆真实环境下，氘氚聚变反应产生的14 MeV高能中子辐照将在材料中产生严重的原子离位损伤和各种缺陷积累。其中自间隙原子（SIA）及其团簇是中子辐照损伤中最常见的缺陷种类。本文采用分子动力学模拟系统研究钨中1/2〈111〉和〈100〉 SIA团簇的稳定结构和形成能，发现SIA团簇最稳定结构是1/2〈111〉 SIA团簇结构，SIA团簇聚集后会稳定存在。并研究了不同尺寸1/2〈111〉 SIA团簇的动力学扩散行为，发现单个SIA在温度高于700 K时易扩散和转向，而两个以上的SIA团簇在300~900 K时主要表现为一维方向的运动。为准确描述各种尺寸SIA团簇的动力学行为，给出了一套计算SIA团簇跃迁频率的经验参数。相关结果将为更大尺度的动力学蒙特卡罗和团簇动力学模拟提供准确和完备的输入参数，为正确掌握和评价钨中子辐照行为提供依据。

Molecular Dynamics Simulation on Diffusion Behavior of Self-interstitial Atom Cluster in Tungsten

Tungsten is considered as the most potential plasma-facing material in the future fusion reactor. However, in the real environment of future fusion reactor, 14 MeV high-energy neutron irradiation produced by deuterium-tritium fusion reaction will cause serious atoms displacement and various defects accumulation in materials. Here, self-interstitial atom and its clusters are the most common defects in neutron irradiation damage situation. Molecular dynamics simulation was used to study the stable structures and formation energy of 1/2〈111〉 and 〈100〉 self-interstitial atom clusters in tungsten. It is found that the most stable structure of SIA cluster in W is 1/2〈111〉 SIA cluster, which would be stable after aggregation. The diffusion behavior of 1/2〈111〉 self-interstitial atom clusters with different sizes was also studied, and it is found that a single SIA cluster is easy to diffuse and turn when the temperature is higher than 700 K, while two or more SIA clusters shows one-dimensional motion when the temperature is 300-900 K. In order to accurately describe the dynamic behavior of SIA clusters of various sizes, a set of empirical parameters for calculating the transition frequency of SIA clusters was presented. The results will provide accurate and complete input parameters for larger-scale simulations such as kinetic Monte Carlo and cluster dynamics, and provide the basis for correctly understanding and evaluating the neutron irradiation behavior in tungsten.