嬗变溶质修饰空洞的第一性原理模型：短程有序效应及其在中子辐照钨中的应用
First principles model for voids decorated by transmutation solutes: Short-range order effects and application to neutron irradiated tungsten
摘要：
了解材料的性质如何因核嬗变而变化是聚变发电厂结构部件设计的主要挑战。在这项研究中，通过结合第一性原理矩阵哈密顿方法与热力学积分，我们调查准稳态配置的多组分合金，含有缺陷，在很宽的温度和组成范围。该模型能够模拟材料中的嬗变引起的偏析效应，包括钨，其中该现象非常明显。等温分析表明，空洞被Re和Os装饰，但没有钽（Ta）的装饰。元素之间的差异与杂质和空位物种之间的短程有序（SRO）参数的符号相关，与原子探针断层扫描（APT）观察辐照W-Re，W-Os，W-Ta合金在固溶体极限一致。对富空位钨中Re和Os杂质的统计分析表明，这两种溶质的自还原效应对物种的背景浓度高度敏感。在含1.5%Re和0.1%Os的四元W-Re-Os-Vac合金中，在1200 K时，SRO Re-Os参数为负值，促使Re和Os的析出集中。与实验的透射电子显微镜（TEM）和APT数据在高通量反应堆（HFR）照射的W样品的比较表明，该模型解释了异常偏析的嬗变产物（Re，Os）的空位簇和空隙的起源在高温限制有关的聚变发电厂的操作条件。
英文摘要：
Understanding how properties of materials change due to nuclear transmutations is a major challenge for the design of structural components for a fusion power plant. In this study, by combining a first-principles matrix Hamiltonian approach with thermodynamic integration we investigate quasi-steady state configurations of multi-component alloys, containing defects, over a broad range of temperature and composition. The model enables simulating transmutation-induced segregation effects in materials, including tungsten where the phenomenon is strongly pronounced. Finite-temperature analysis shows that voids are decorated by Re and Os, but there is no decoration by tantalum (Ta). The difference between the elements is correlated with the sign of the short range order (SRO) parameter between impurity and vacancy species, in agreement with Atom Probe Tomography (APT) observations of irradiated W-Re, W-Os, W-Ta alloys in the solid solution limit. Statistical analyses of Re and Os impurities in vacancy-rich tungsten show that the SRO effects involving the two solutes are highly sensitive to the background concentration the species. In quaternary W-Re-Os-Vac alloys containing 1.5% Re and 0.1% Os, the SRO Re-Os parameter is negative at 1200K, driving the formation of concentrated Re and Os precipitates. Comparison with experimental Transmission Electron Microscopy (TEM) and APT data on W samples irradiated at the High Flux Reactor (HFR) shows that the model explains the origin of anomalous segregation of transmutation products (Re,Os) to vacancy clusters and voids in the high temperature limit pertinent to the operating conditions of a fusion power plant.
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