Ans: It is given that the density of niobium,
Atomic mass,
As the lattice is bcc type, the number of atoms per unit cell,
Let the edge length of the unit cell be ‘ and the length of the face diagonal be b.
From , we have:
Let be the radius of the atom.
Now, from the figure, it can be observed that:
Now, volume of the cube,
We know that the number of atoms per unit cell is
So, volume of the occupied unit cell
Therefore, packing efficiency
Therefore, packing efficiency in face centered is .