分子动力学模拟C＋离子与聚变材料钨的相互作用

Molecular Dynamic Simulation of Interaction of C^+ Ions and Fusion Material Tungsten

采用分子动力学方法模拟不同能量的C+离子与聚变材料钨的相互作用。模拟结果表明:当C+离子入射剂量为3.11×1016cm-2,入射能量为50 eV时,样品表面形成一层碳膜;而入射离子能量为150和250 eV时,C+离子入射到样品内与钨原子共同形成碳钨混合层,样品表面没有形成碳膜;碳的沉积率随能量的增大先减小后增加,溅射率随能量的增大先增大后减小;轰击后的样品中,碳原子密度、C-W键密度及C-C键密度分布都随能量的增加逐渐向样品内移动,且C-W键分布厚度随能量的增加而逐渐增加,C-C键分布厚度几乎不随能量变化;在作用过程中极少量的钨原子发生溅射,但引起钨晶格损伤严重;碳在轰击后的样品中主要以Csp3杂化形式存在。

The interaction of the impinging C＋ ion beam and the fusion material W was modeled and simulated, based on molecular dynamics, to understand the possible mechanisms responsible for the carbon deposition and carbon ion sputtering of W surface in fusion. The impacts of the interaction conditions, including the incident C＋ energy and expo- sure, on the interaction were simulated. The simulated results show that the carbon atom exists mainly in sp3 state on W surfaces, and that the energy of incident C ~ strongly affects the deposition and sputtering rates. For example, as the energy increases, the deposition rate of C varies in a decrease-increase mode;whereas the sputtering rate changes in an increase- decrease mode. At an energy of 50 eV and an exposure of 3.11 ×1016 cm- 2, a thin carbon membrane forms on W sur- face,at an energy of 150 eV and 250 eV,carbon atoms are implanted in top layers of W,no carbon membrane can be ob- served. As the energy increases, the peaks of the depth profiles of C-W and C-C bonds move deeper inside W, with an in- creasingly thicker layer of C-W bond and a thickness unchanged layer of C-C bend. The sputtering of W, rarely occurs though, may seriously damage the lattice.