A correlation-based model-free method for tracking structural changes in in situ X-ray diffraction datasets

In situ X-ray diffraction (XRD) measurements are widely used to investigate structural changes and often generate large XRD datasets. Although principal component analysis (PCA) and Rietveld refinement are effective tools for data analysis, they generally require additional physical interpretation or structural models, making the screening of large datasets challenging. To address this challenge, we propose a model-free method based on time-dependent correlation functions for directly tracking structural changes in large in situ XRD datasets without requiring crystallographic models or profile fitting. The effectiveness of the proposed method was demonstrated using in situ XRD datasets collected during the amorphization of zeolites over a temperature range from room temperature to 1000 °C. The proposed method successfully tracked dehydration and amorphization processes directly from in situ XRD datasets and showed good agreement with the trends observed in differential thermal analysis (DTA) and thermogravimetry (TG) measurements. These results demonstrate that the proposed method provides a practical tool for screening and tracking structural changes in large in situ XRD datasets.