Wurtzite 5: holes in the structure

We can think of the zinc ions occupying holes in the hexagonal close packed array of sulfide ions. Inspection of the zinc ion that resides wholly in the unit cell shows that its four sulfide neighbours lie on the corners of a tetrahedron with the zinc ion at its centre. This is shown on the left with a green tetrahedral wireframe. In the zinc blende lattice we saw that there is a 2:1 ratio of tetrahedral holes to the close-packed sulfide ions, and that half of these tetrahedral holes are occupied by zinc ions. It is a similar situation in wurtzite. The empty tetrahedral hole that partners the occupied one shown in green is illustrated on the left with the violet wireframe.

Holes and stoichiometry:

In wurtzite the unit cell occupancy of sulfide is 2. Because of the 1:1 stoichiometry of zinc and sulfur there should be two occupied tetrahedral holes in the unit cell. Only one tetrahedral hole is indicated on the left. It is easier to appreciate the other hole in this hexagonal unit cell by returning to the bulk structure.

Go to page 6 to focus on the remaining tetrahedral holes that are visible in the bulk structure.

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