Question

‘C’ represent the height of the HCP unit cell and ‘a’ represent edge length of the hexagonal surface of the HCP unit cell. What is the value of C/a ?

• A. $\sqrt{\frac{2}{3}}$
• B. $\sqrt{\frac{8}{3}}$
• C. $\sqrt{\frac{32}{3}}$
• D. $\sqrt{\frac{3}{2}}$

Answer 1

Answer: (B)

$\sqrt{\frac{8}{3}}$

Answer 2

In HCP unit cell

C = 4r $\sqrt{\frac{2}{3}}$

a = 2r

$\therefore$ $\frac{c}{a}$ = $2\sqrt{\frac{2}{3}}$ = $\sqrt{\frac{8}{3}}$