Prototype Index

• This is an index of the various crystal structures by prototype compound. Note that these are in the logical alphabetical order. Thus what is usually called Cu₃Au is listed as AuCu₃, and rock salt as ClNa.
• Hypothetical compounds such as BCT5 are listed with their proposed constituents (here, Si). If an element or compound is associated with more than one prototype the most common prototype is listed first.
• The column labeled Wyckoff Positions shows those positions which the structure occupies in its space group. A superscript, e.g. ae³, indicates that multiple groups of atoms occupy the indicated Wyckoff position, with, of course, different values for the parameters. In principle, structures with the same space group and occupied Wyckoff positions could transform into one another by a continuous transformation, i.e., without a phase transformation. However, in some cases this may be prohibited by geometric or physical considerations.

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