Question

Niobium has a density of 8.57 g/cm³ and crystallizes with the body-centered cubic unit cell. Calculate the radius of a niobium atom.

Answer 1

Effective no. of atom in a unit cell is determined by how much fraction of atom is contained in a unit cell. All the atoms at corners contribute only 1/8th, atoms at face center contribute 1/2 while an atom at body center is fully inside that unit only.

Hence for a bcc unit cell, effective no. of atom= 8*(1/8) + 1*(1)=2