Question

Copper has face-centred cubic (fcc) lattice with interatomic spacing equal to $ 2.54 \, \mathring{A}$ . The value of lattice constant for this lattice is

• A. $1.27 \mathring{A}$
• B. $5.08 \mathring{A}$
• C. $2.54 \mathring{A}$
• D. $3.59 \mathring{A}$

Answer 1

Answer: (D)

Interatomic spacing for fcc lattice
$r=\left[\left(\frac{a}{2}\right)^{2}+\left(\frac{a}{2}\right)^{2}+(0)^{2}\right]^{1 / 2}=\frac{a}{\sqrt{2}}$
a being lattice constant.
$\therefore a=\sqrt{2} r=\sqrt{2} \times 2.54=3.59 \,\mathring{A}$