Chemistry - Solid State Question with Solution | TestHub

The correct option is B. This describes the rhombohedral (or trigonal) crystal system, which has $a=b=c$ and $\alpha =\beta =\gamma \ne 90^{\circ }$. It can only have a primitive (P) Bravais lattice.

Crystal systems and their Bravais lattices:

1. Cubic: $a=b=c$, $\alpha =\beta =\gamma =90^{\circ }$. P, I, F

2. Tetragonal: $a=b\ne c$, $\alpha =\beta =\gamma =90^{\circ }$. P, I

3. Orthorhombic: $a\ne b\ne c$, $\alpha =\beta =\gamma =90^{\circ }$. P, C, I, F

4. Hexagonal: $a=b\ne c$, $\alpha =\beta =90^{\circ }$, $\gamma =120^{\circ }$. P

5. Rhombohedral (Trigonal): $a=b=c$, $\alpha =\beta =\gamma \ne 90^{\circ }$. P

6. Monoclinic: $a\ne b\ne c$, $\alpha =\gamma =90^{\circ }$, $\beta \ne 90^{\circ }$. P, C

7. Triclinic: $a\ne b\ne c$, $\alpha \ne \beta \ne \gamma \ne 90^{\circ }$. P