Data and code for selective band-gap prediction of lead-free A₂BB′X₆ halides under unseen B-site chemistry

This record contains the processed data, source identifiers, group assignments, out-of-fold predictions, robustness and selective-prediction analyses, plotting code, environment specifications, verification scripts, and curated DFT evidence supporting the manuscript “Selective Band-Gap Prediction for Lead-Free A₂BB′X₆ Halides under Unseen B-Site Chemistry.” The frozen modelling table contains 1,931 Pb-free records, 1,898 formulas, and 353 unordered B/B′ pairs. Author-written code is released under the MIT License. Original tables, documentation, and author-generated analysis outputs are released under CC BY 4.0. Materials Project and JARVIS-derived records and literature transcriptions retain the rights and attribution requirements of their original sources. Licensed VASP POTCAR files and large restart files are not included.