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MINERALS AND SYNTHETIC COMPOUNDS, A_mX_n, IN WHICH X ATOMS ARE

CLOSE PACKED AND A ATOMS OCCUPY TETRAHEDRAL INTERSTICES

Zincblende

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tetra	50%	fcc	3-d	4 vertices	A- 4c, X- 4c/fcc

structure

The zincblende structure has A atoms occupying fifty percent of the tetrahedral

interstices in each successive layer of FCC packed X atoms. This structure is also

called sphalerite.

Ex. ZnS ( zinc sulfide, zincblende ) - low temperature polymorph ( Zn - A , S - X )

Crystal lattice

In the FCC lattice model the AX₄ groups of sulfur atoms that are tetrahedrally

coordinated with zinc atoms residing in their interstitial voids are colored differently

than the tetrahedral or octahedral clusters of sulfur atoms whose voids are

unoccupied (blue).

The lattice model shows that the AX₄ coordination groups of atoms are joined

by their vertices only due to the fact that only fifty percent of the tetrahedral voids

of each layer are occupied.

Polyhedral framework

.
linking surfaces
		Figure 61 - Zincblende polyhedral
		framework model
		( 50 T, 60 pinges)
4 vertices
.

The polyhedral framework model clearly shows that 50% of the tetrahedrally

coordinated groups of X atoms are occupied with A atoms. The structure is built up

by linking all the vertices of these tetrahedra together. By convention only the

occupied tetrahedra are modeled to highlight the geometry and symmetry of these

AX₄ coordinated groups of cations and anions.

Cleavage
(110) - perfect		truncated tetrahedron
		( 28 T, 42 pinges )
Crystal habit
tetrahedral, dodecahedral, twinning on (111)
.

Isostructural minerals/compounds

AgI, AlAs, AlP, AlSb, BAs, BN, BP, BePo, BeS, BeSe, BeTe, CdPo, CdS, CdSe, CdTe,

CuBr, CuCl, CuF, CuI, GaAs, GaP, Cu₂Fe₂S₄, Cu₂FeSnS₄, GaSb, HgS, HgSe, HgTe,

InAs, InP, InSb, MnS, MnSe, SiC, ZnPo, ZnSe, ZnTe

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Page 43 - Structure matters - Zincblende