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MINERALS AND SYNTHETIC COMPOUNDS, AmXn, IN WHICH X
ATOMS ARE |
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CLOSE PACKED AND A ATOMS OCCUPY OCTAHEDRAL INTERSTICES |
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NiAs |
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click here to see a key to this data bar
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octa |
100% |
hcp |
3-d |
2
faces, 6 edges |
A-
6c, X- 6c/hcp |
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structure |
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The NiAs structure is
comprised of HCP packed X atoms with A atoms occupying |
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100% of the octahedral interstitial voids in
each successive close packed layer. |
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Ex. NiAs ( nickel arsenide, niccolite
or nickeline ) ( Ni - A , As - X ) |
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Crystal lattice |
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Since all of the
octahedral voids are occupied the crystal can be modeled as |
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a simple HCP lattice with all of the
AX6
coordination groups in a layer colored the |
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same color. The eclipsed arrangement of
these groups in each successive layer |
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is evident by the lattice. |
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Figure 75 - NiAs lattice structure |
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click image to enlarge |
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Polyhedral framework |
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linking surfaces |
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Figure 76 - NiAs polyhedral |
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framework model |
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( 66 T, 81 pinges) |
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2
faces, 6 edges |
click image to enlarge |
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The polyhedral
framework demonstrates that the AX6 octahedral coordination |
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groups stack together in the HCP configuration
so that each shares two faces and |
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six edges with adjacent groups. Compare
this structure with halite which is FCC. |
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Cleavage |
Crystal habit |
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none |
pyramidal (rare) |
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Isostructural minerals/compounds |
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AuSn, CoS, CoSb, CoSe, CoTe, CrSb, CrSe, CrTe,
CuSn, FeS, FeSb, FeSe, FeTe, |
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IrSb,
IrTe,
MnAs, MnBi, MnSb, MnTe, NiSb, NiSe, NiTe, PdSb, PdTe, PtB, PtSb, PtSn, |
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RhBi, RhTe, ScTe, TiS, TiSe, TiTe, VP, VS, VSe,
ZrTe |
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Page
51 - Structure matters - NiAs |
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