FCC Crystal Problem: Nearest Neighbors, Bond Angles & Packing Fraction

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Homework Statement



Write down the number of nearest neighbours in a FCC structure, calculate the angle between the bonds and the packing fraction.

Homework Equations



Literally don't know where to start!

The Attempt at a Solution



Very confused at the moment. Tried to look up packing fraction in my Solid State texbook - but it isn't there?! Is there another name for it? Can someone point me in the right direction please? :)
 
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ok - could someone validate my answer please?

i got 4 atoms in one crystal,

the volume of one atom: ( pi * (2^(3/2)) * (a^3) ) / 48

the volume of the crystal is a^3

giving a packing fraction of 0.236?
 
Check your math.
 

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