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Octahedral and Tetrahedral sites, fcc Crystal |
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The
two diagrams show the coordination figures for Octahedral and Tetrahedral
sites in an fcc crystal structure. The fcc crystal has four lattice points
associated with the unit cell, and using the same fractional counting for
the Octahedral sites (O) gives four such sites associated with the unit
cell. For a basis of one atom, the atom to octahedral site ratio is 1 :
1, i.e. there are as many octahedral sites as atoms on fcc lattice points.
The lower diagram illustrates one of the tetrahedral sites in the fcc structure.
One such site (T) is associated with each corner atom of the unit cell
for a total of 8 tetrahedral sites per cell. The site to lattice point
ratio is therefore 2 : 1 for this case. |
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After:
Chiang, Birnie III, and Kingery, "Physical Ceramics," Wiley (1997) |
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