MINERALS AND SYNTHETIC COMPOUNDS, AmXn, WITH CLOSE PACKED

X ATOMS AND A ATOMS OCCUPYING TRIGONAL PRISMATIC INTERSTICES
 
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AlB2

                  click here to see a key to this data bar                                  

trigonal prismatic

100%

hp

3-d

all faces

A- 6c, X- 12c/hp
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  structure

 .
. .
     In the AlB2 structure the X atoms are close packed in the HP arrangement (simple .
hexagonal or hexagonal primitive) and the A atoms occupy 100% of the trigonal .
prismatic interstices.
  .
Ex. AlB2         ( Al - A , B - X ) .
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Crystal lattice
     The crystal structure can be modeled as an HP lattice.  Each hexagonal prism is
sectioned into six trigonal prisms.
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AlB2.gif

  
     Figure 115 -  AlB2 lattice structure

click image to enlarge

                     
   
 
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Polyhedral framework
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linking surfaces

AlB2.gif

  

         Figure 116 -  AlB2 polyhedral
                 framework model
            ( 30 T, 35 S,  78 pinges )

all faces

                        click image to enlarge
.      
     The face to face linkage of the trigonal prismatic AX6 coordination groups is
demonstrated by the polyhedral framework.  The close packed X atoms are located
at the vertices of the trigonal prism and the A atoms reside in the void formed in the
center of these six atoms.
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