Step 1: Packing efficiency of BCC unit cell
- Packing efficiency of BCC unit cell is given by,
\(\begin{aligned}
& \text { Packing efficiency }=\frac{\text { Volume occupied by two spheres } \times 100}{\text { Volume of unit cell }} \\
& =\frac{2 \times \frac{4}{3} \pi r^3 \times 100}{a^3} \\
& =68 \%
\end{aligned}\)
- The \(\%\) volume occupied by atoms in a unit cell is \(68 \%\)
Step 2: % Vacant space in BCC unit cell
- % vacant space is given by,
\(\begin{aligned}
& \% \text { Vacant space }=100-\% \text { of the volume occupied by atoms } \\
& =100-68 \\
& =32 \%
\end{aligned}\)
- % Vacant space is \(32 \%\)