Question

Vacant space in $bcc,fcc$ and simple cubic lattice respectively are:
[0.77 Mark]

• A. $46.6\text{\%},26\text{\%}$ and $32\text{\%}$
• B. $26\text{\%},32\text{\%}$ and $52.4\text{\%}$
• C. $68\text{\%},74\text{\%}$ and $52.4\text{\%}$
• D. $32\text{\%},26\text{\%}$ and $47.6\text{\%}$

Answer 1

The correct option is D $32\text{\%},26\text{\%}$ and $47.6\text{\%}$

The packing efficiency of $bcc$ lattice $=68\text{\%}$
So, the vacant space $=100–68=32\text{\%}$
The packing efficiency of fcc lattice $=74\text{\%}$
So, the vacant space $=100–74=26\text{\%}$
The packing efficiency of simple cubic lattice $=52.4\text{\%}$
So, the vacant space $=100–52.4=47.6\text{\%}$