Wurtzite crystal structure
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The wurtzite crystal structure, named after the mineral wurtzite, is a crystal structure for various binary compounds. It is an example of a hexagonal crystal system. The chemical prototype is conventionally given as ZnS, although mineral wurtzite is a multi-component alloy compound.
The wurtzite crystal structure is referred to by the Strukturbericht designation B4 and the Pearson symbol hP4. The corresponding space group is No. 186 (in International Union of Crystallography classification) or P63mc (in Hermann–Mauguin notation).
Among the compounds that can take the wurtzite structure are wurtzite itself, AgI, ZnO, CdS, CdSe, α-SiC, GaN, AlN, w-BN and other semiconductors. In most of these compounds, wurtzite is not the favored form of the bulk crystal, but the structure can be favored in some nanocrystal forms of the material.
Each of the two individual atom types forms a sublattice which is HCP-type (short for "hexagonal close-packed"). When viewed altogether, the atomic positions are the same as in lonsdaleite (hexagonal diamond). Each atom is tetrahedrally coordinated.
The wurtzite structure is non-centrosymmetric (i.e., lacks inversion symmetry). Due to this, wurtzite crystals can (and generally do) have properties such as piezoelectricity and pyroelectricity, which centrosymmetric crystals lack.