Polymorphism of elements and inorganic compounds

Berzelius (1844) introduced the term allotropy as the phenomenon of polymorphism in elements. There has been some debate about the necessity of a special term to designate the polymorphism of elements, as opposed to compounds (Sharma 1987 Reinke et al. 1993), but the term is still introduced in first year chemistry texts, so it has become part of the chemical language. Sharma (1987) has given some examples 

The inorganic equivalent of the CSD is the Inorganic Crystal Structure Database (ICSD) (FIZ 2001 Bergerhoff et al. 1983). This currently contains over 53000 entries (August 2000) with two updates per year, and may be searched in a manner similar to that used for the CSD. There are currently efforts under way to unify the searching software for these two important data bases, a move which would considerably facilitate and widen their use. Another useful source is the inorganic section of the PDF (ICDD 2001 Jenkins and Snyder 1996). For older references, the first two volumes of Groth (1906, 1908) are particularly valuable. 

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