利用变形材料的原子模型验证X射线线型缺陷分析
Validating x-ray line-profile defect analysis using atomistic models of deformed material
摘要：
晶体材料中位错缺陷的数量强烈影响其性能，因此在实验样品中分析该数量的能力具有很大的实用性。作为透射电子显微镜直接计数的补充，X射线衍射线轮廓的定量分析是一种重要的工具。这是一种间接的量化方法，因此需要仔细验证推理过程中的物理模型。在这里，我们进行直接评估的能力，线轮廓分析，量化方面的位错和堆垛层错人口利用变形铜单晶的原子模型。我们直接分析这些模型，以确定缺陷内容的确切细节（我们的“地面实况”）。然后，我们生成的模型和分析它们使用相同的程序在实验分析中使用的理论线轮廓。这导致我们能够与确切数据进行比较的缺陷含量的推断测量。我们表明，线轮廓分析是能够提供良好的预测位错密度和堆垛层错分数跨越两个数量级。我们进一步展示了沃伦和阿弗巴赫所调用的位错分布的均方应变中的外截止半径如何对应于根据Wilkens模型人工构建的位错的限制随机分布中的晶胞尺寸。总体而言，我们的研究结果提供了重要的新的支持，使用线轮廓分析的量化晶体材料中的线和平面缺陷。
英文摘要：
The population of dislocation defects in a crystalline material strongly influences its properties, so the ability to analyse this population in experimental samples is of great utility. As a complement to direct counting in the transmission electron microscope, quantitative analysis of x-ray diffraction line profiles is an important tool. This is an indirect approach to quantification and so requires careful validation of the physical models that underly the inferential process. Here we undertake to directly evaluate the ability of line profile analysis to quantify aspects of the dislocation and stacking fault populations by exploiting atomistic models of deformed copper single crystals. We directly analyse these models to determine exact details of the defect content (our "ground truth"). We then generate theoretical line profiles for the models and analyse them using the same procedures used in experimental analysis. This leads to inferred measures of the defect content which we are able to compare with the exact data. We show that line profile analysis is able to provide sound predictions of both dislocation density and stacking fault fraction across two orders of magnitude. We further show how the outer cut-off radius in the mean-square strain of a dislocation distribution invoked by Warren and Averbach corresponds to the cell size in an artificially constructed restrictedly-random distribution of dislocations according to the model of Wilkens. Overall, our results lend important new support to the use of line profile analysis for the quantification of line and planar defects in crystalline materials.
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