: It integrates physical, chemical, and crystallographic data, allowing for Rietveld analysis and electron diffraction simulations. : It is sold as a limited-term license

If you work in , you’ve probably heard the term ICDD PDF‑4 pop up in forums, research papers, and tech newsletters. The “ICDD PDF‑4 Database” is a specialized collection of PDF documents and metadata curated for testing, benchmarking, and developing PDF‑related tools—especially those that deal with document classification, OCR, content extraction, and digital preservation .

: This is the most popular free alternative. It contains hundreds of thousands of entries for organic, inorganic, and metal-organic compounds. Most modern XRD software can import COD data. American Mineralogist Crystal Structure Database (AMCSD)