In particular the orientation of the (100) and (111) planes of the FCC lattice can be .
modeled to relate the nature of their interpenetration. .

click to enlarge

Figure 43 - Interpenetrating FCC
         (100) and (111) layers
            ( 72 T, 79 pinges )
                click image to enlarge


     Slicing the FCC lattice parallel to each of the (100), (110), and (111) planes also .
demonstrates the orientation of these symmetry planes and the geometry of their .
sphere (atom) packings.  In the following model the red (100) plane is shown to .
intersect with the blue (110) plane and the purple (111) plane at a corner. .

     Figure 44 - (100), (110), and (111)
         surfaces of the FCC lattice
     The atomic packing arrangement of the differently oriented layers in matter .
relates to the external forms, or habits, their crystals commonly exhibit as well as the
crystals' cleavage planes and surface physical characteristics.  In particular, a
discrete crystal is built up by the sequential layering of atoms on its exposed surface.
Thus the internal structure of its crystal lattice greatly influences its external
appearance.  For example the above image can be pictured as a corner of a crystal
with an FCC lattice structure.  Also the cleavage planes of crystals often parallel the
closest packed (111) plane.  Some crystals even exhibit differential hardness with the
densest packed (111) face being the hardest.  Finally, the surface reactivity of some
catalytically important precious metals is dependent on what surface is exposed
when they are cut or etched.
     As will be seen in the following section, atoms can avail themselves of the
periodic regularity afforded by the CP, HP, FCC, HCP, BCC, and other uniform lattice
structures to create a rich diversity of inorganic matter which varies widely in
chemical and physical properties.

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Page  30 -  Structure matters - FCC symmetry

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