Bilbao crystallographic server: Useful databases and tools for phase-transition studies

The Bilbao Crystallographic Server is a web site with crystallographic programs and databases available on-line. The programs give access to general information related to space groups (generators, general positions, Wyckoff positions, irreducible representations), group-subgroup or group-supergroup pairs of space groups, and/or results on specific crystal structures. The utility of the programs is illustrated by treating phase-transition problems related to structural pseudosymmetry. The programs can be accessed through the main page of the server (www.cryst.ehu.es) and can be used free of charge with any web browser.