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  Structure Compound     3 of 4

We shall now consider compounds, i.e. more than one atom at each lattice point and atoms of different types. The scattering factor for each atom in the unit cell is not the same, since the atoms are not the same. This can lead to a structure factor which depends on composition.

Have a go imageConsider the compound ZnS (sphalerite). Sulphur atoms occupy fcc sites with zinc atoms displaced by from these sites. Click on the animation opposite to show this structure. The unit cell can be reduced to four atoms of sulphur and 4 atoms of zinc.

Many important compounds adopt this structure. Examples include ZnS, GaAs, InSb, InP and (AlGa)As. Diamond also has this structure, with C atoms replacing all the Zn and S atoms. Important semiconductor materials silicon and germanium have the same structure as diamond.



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