Question

Which type of crystal contains more than one Bravais lattice?
A.Hexagonal
B.Triclinic
C.Rhombohedral
D.Monoclinic

Answer 1

Bravais lattices refers to the configurations into which atoms can be arranged in crystals. There are $14$ Bravais lattices in three dimensional systems.

Complete step by step answer:
Lattice system is a group of lattices containing the same set of lattice point groups. There are $14$ Bravais lattices in total. These $14$ Bravais lattices are divided into $7$crystal systems.
The $7$crystal systems along with their Bravais lattices are listed in the table.

Sl No.	Crystal system	Number of Bravais lattices	Types of Bravais lattices
$1$	Cubic	$3$	primitive, body centered, face centered
$2$	Tetragonal	$2$	primitive, body centered
$3$	Hexagonal	$1$	primitive
$4$	Rhombohedral	$1$	primitive
$5$	Orthorhombic	$4$	primitive, body centered, face centered, end centered
$6$	Monoclinic	$2$	primitive, end centered
$7$	Triclinic	$1$	primitive

The given options contain hexagonal, triclinic, rhombohedral and monoclinic. From the above table, it is clear that, hexagonal, triclinic and rhombohedral crystal systems contain only one Bravais lattice. That one Bravais lattice corresponds to a primitive cell. But the monoclinic crystal system contains two Bravais lattices. These two Bravais lattices are primitive and end centered unit cells. Hence the crystal system which contains more than one Bravais lattice is monoclinic.
Hence the correct option is D.

Note:
Monoclinic system contains primitive and end centered unit cells. The primitive unit cell contains particles only at the eight corners. But the end centered unit cell contains particles in all corners as well as in two opposite faces. Total number of particles in the primitive unit cell is $1$ and that in the end centered unit cell is $2$.