We report a systematic energetic analysis of helium-related defect interactions that mediate helium (He) segregation on surfaces of plasma-exposed tungsten at different levels of He ion implantation. We focus on high He fluences that increase the He content in the plasma-exposed material well beyond the dilute limit of He concentration and employ atomic configurations generated by large-scale molecular dynamics simulations of He-implanted tungsten. We perform systematic molecular statics computations of cluster–defect interaction energetics in the highly defect-rich near-surface region of plasma-exposed tungsten for small mobile helium clusters as a function of the clusters' distances from the surface. In this region, mobile clusters are also subjected to the stress fields generated by defects such as helium bubbles and other clusters, which govern cluster–defect interactions in addition to the cluster–surface interaction. Based on systematic investigation of individual cluster–defect interactions, we develop a mathematical framework to describe the interaction energy landscapes consisting of elastic interaction potential perturbations to finite-width square-well potentials, where the potential well accounts for cluster trapping by the defect at close range and subsequent coalescence and the perturbation potential is parameterized according to elastic inclusion theory. Superposition of all the relevant interaction potentials provides a comprehensive description of the interaction energy landscape that would be experienced by a small mobile cluster along its migration path toward the plasma-exposed surface at high He fluences. Such descriptions are particularly important for developing atomistically informed, hierarchical multi-scale models of helium cluster dynamics in plasma-facing materials.

中文翻译：

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等离子体暴露钨的近表面区域中与非稀氦相关的缺陷相互作用

我们报告了对氦相关缺陷相互作用的系统能量分析，这些相互作用在不同水平的 He 离子注入下介导了等离子​​体暴露的钨表面上的氦 (He) 偏析。我们专注于高 He 能量密度，这会增加暴露于等离子体的材料中的 He 含量，远远超出 He 浓度的稀释极限，并采用由注入 He 的钨的大规模分子动力学模拟产生的原子配置。我们在等离子体暴露的钨的高度缺陷丰富的近表面区域中对小的移动氦簇执行簇-缺陷相互作用能量的系统分子静力学计算，作为簇与表面距离的函数。在该区域，移动团簇也受到氦气泡等团簇等缺陷产生的应力场的作用，除了簇-表面相互作用之外，它们还控制簇-缺陷相互作用。基于对单个簇-缺陷相互作用的系统研究，我们开发了一个数学框架来描述由弹性相互作用势扰动到有限宽度方阱势组成的相互作用能量图谱，其中势阱解释了由缺陷在关闭时捕获的簇。范围和随后的合并和扰动势根据弹性包含理论进行参数化。所有相关相互作用势的叠加提供了对相互作用能量景观的全面描述，小型移动星团在高氦通量下沿着其向等离子体暴露表面的迁移路径将经历这种情况。