Question

In a monoclinic unit cell, the relation of sides and angles are respectively :

• A. $a = b \ne c$ and $\alpha = \beta = \gamma= 90^{\circ}$
• B. $a \ne b \ne c$ and $\alpha = \beta = \gamma= 90^{\circ} \ne \alpha$
• C. $a \ne b \ne c$ and $\beta = \gamma= 90^{\circ} \ne \alpha$
• D. $a \ne b \ne c$ and $\alpha \ne \beta \ne\gamma\ne 90^{\circ}$

Answer 1

Answer: (C)

$a \ne b \ne c$ and $\beta = \gamma= 90^{\circ} \ne \alpha$

Answer 2

Monoclinic crystal is one of the $7$ crystal system. In monoclinic system, the crystal is describe by vectors of unequal lengths,
So, we have $a \neq b \neq c$ and $\beta=\gamma=90^{\circ} \neq \alpha$