: Some specialized versions, like PDF-4/Minerals or PDF-4/Axiom , include the SIeve+ search-indexing software for free with the purchase of the database license. Free Alternatives for Crystallographic Data
An open-access initiative funded by the U.S. Department of Energy. Icdd Pdf-4 Database Free Download
True PDF-4 databases require a physical USB dongle or a secure network license to operate. A simple "downloaded file" will not work without this hardware or server verification. : Some specialized versions