Question

The fraction of edge covered by atoms in $bcc$ unit cell is :-

• A. $0.32$
• B. $0.866$
• C. $0.134$
• D. $0.268$

Answer 1

Answer: (B)

$BCC$ unit cell : $\sqrt{3}a=4r$
$a=\frac{4r}{\sqrt{3}}$
Length of covered edge $=r+r=2r$
Fraction $=\frac{2r}{\frac{4r}{\sqrt{3}}}=\frac{\sqrt{3}}{2}=\frac{1.732}{2}=0.866$