Question

The crystal system of a compound with unit cell dimensions $a=0.387,b=0.387,c=0.504nm$ and $\alpha =\beta ={90}^{\circ }$ and $\gamma ={120}^{\circ }$ is:

• A. cubic
• B. hexagonal
• C. orthorhombic
• D. rhombohedral

Answer 1

The correct option is B hexagonal

The crystal system of a compound with unit cell dimensions:

$a=0.387,b=0.387,c=0.504nm$, $\alpha =\beta ={90}^{\circ }$ and $\gamma ={120}^{\circ }$ is hexagonal.

The dimensions are $a=b\ne c$ and $\alpha =\beta =$ $\gamma$.
Note :
For cubic crystal, the dimensions are $a=b=c$ and $\alpha =\beta =\gamma ={90}^{\circ }$
For orthorhombic crystal, the dimensions are $a\ne b\ne c$ and $\alpha =\beta =\gamma ={90}^{\circ }$
For rhombohedral crystal, the dimensions are $a=b=c$ and $\alpha =\beta =\gamma \ne {90}^{\circ }$