Question

Calculate the volume of the unit cell for fcc Pb given that its atomic radius is 0.175 nm.

Answer 1

if fcc edge length a= 2 x square root of 2 x r
edge length a = 2x square root of 2 x r(radius)
                       = 2 x 1.414 x 0.175
                       = 0.4949
volume = a^3
             = 0.4949^3
             = 0.121 nm^3
             
              

Answer 2

For fcc edge length (a) and Atomic radius (r) is related as
a = 2√2 × r

a = 2√2 × 0.175 nm
= 0.49 nm

Volume of cubic unit cell = a³
= (0.49)³
≈ 0.12 nm³
= 120 ų