无需标注数据,用机器学习自动识别材料辐照缺陷并分类。
Unsupervised Machine-Learning Pipeline for Data-Driven Defect Detection and Characterisation: Application to Displacement Cascades
- 用SOAP编码原子环境,通过自编码器找异常原子。
- 99.7%异常原子被归入紧凑物理结构,聚类结果与缺陷数量强相关。
- 无需调参,可替代传统检测方法,适合辐照损伤研究者。
中子辐照在数皮秒内产生位移级联,引发一系列原子碰撞,形成点缺陷和扩展缺陷,影响材料长期演化。本文提出一种完全无监督的机器学习流程,直接从分子动力学数据中检测并分类这些缺陷。原子局部环境由光滑原子位置重叠(SOAP)向量编码,异常原子通过自编码器(AE)识别,再经均匀流形近似与投影(UMAP)嵌入,并用层次密度聚类(HDBSCAN)分组。该方法应用于80 keV下镍、Fe₇₀Ni₁₀Cr₂₀和锆中的位移级联,结果显示自编码器成功识别参与缺陷形成的少量异常原子;HDBSCAN将AE标记的SOAP特征嵌入空间划分为明确区域,区分空位主导区与间隙原子主导区,并进一步分离小簇与大团簇,99.7%的异常原子被正确分配至紧凑物理结构。带符号的聚类识别评分验证了这一分离效果,聚类大小与净缺陷数量高度相关(R² > 0.89)。ML异常图与传统检测器(如中心对称性、位错提取等)进行统计交叉分析,显示强重叠与互补覆盖,且全程无需模板或阈值调整。该方法为材料中结构异常的定量映射提供了高效工具,尤其适用于辐照损伤引起的位移级联研究。
原文摘要 · Abstract (English)
Neutron irradiation produces, within a few picoseconds, displacement cascades that are sequences of atomic collisions generating point and extended defects which subsequently affects the long-term evolution of materials. The diversity of these defects, characterized morphologically and statistically, defines what is called the "primary damage". In this work, we present a fully unsupervised machine learning (ML) workflow that detects and classifies these defects directly from molecular dynamics data. Local environments are encoded by the Smooth Overlap of Atomic Positions (SOAP) vector, anomalous atoms are isolated with autoencoder neural networks (AE), embedded with Uniform Manifold Approximation and Projection (UMAP) and clustered using Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN). Applied to 80 keV displacement cascades in Ni, Fe$_7$0Ni$_{10}$Cr$_{20}$, and Zr, the AE successfully identify the small fraction of outlier atoms that participate in defect formation. HDBSCAN then partitions the UMAP latent space of AE-flagged SOAP descriptors into well defined groups representing vacancy- and interstitial-dominated regions and, within each, separates small from large aggregates, assigning 99.7 % of outliers to compact physical motifs. A signed cluster-identification score confirms this separation, and cluster size scales with net defect counts (R2 > 0.89). Statistical cross analyses between the ML outlier map and several conventional detectors (centrosymmetry, dislocation extraction, etc.) reveal strong overlap and complementary coverage, all achieved without template or threshold tuning. This ML workflow thus provides an efficient tool for the quantitative mapping of structural anomalies in materials, particularly those arising from irradiation damage in displacement cascades.
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