Question

Describe the bcc unit cell and hence determine the packing fraction

Answer 1

Bcc unit cell can be described as,,,
___ if an atom present at the body centre, it is not shared by any other unit cell. so that one atom completely belongs to same unit cell.

packing fraction :---__
packing fraction, the fraction of volume occupied by the spheres in the structure.

✴️ Packing fraction = V(sphere) / V(unit cell)
      = 2×4/3 p R3 / (4/sqrt(3) R3)
      = 3 p / 8 = 0.6802.