Lattice points
at the corners
of the parallelepiped
and at
the centre of each face of the unit cell.
I type
F type
Bodycentered Lattice
Facecentered Lattice
Bodycentred/Facecentred
Effective number of Lattice points / cell=
= [1 (for corners)] + [1 (BC)] =
2
Effective number of Lattice points / cell=
= [1 (for corners)] + [6
(1/2)] =
4

06-02-2020
15
Seven systems lead to
28
crystal structures:14 Bravais lattices
1.
Triclinic (
a ≠ b≠c
and
a
≠
b
≠
≠ 90)
P
,
C, I, F
2.
Monoclinic (
a ≠ b≠c
and
a
=
=90 ≠
b
)
P, C,
I, F
3.
Orthorhombic (
a ≠ b≠c
and
a
=
b
=
=90
)
P
,
C, I, F
4.
Trigonal/Rhombohedral (
a=b=c
&
a
=
b
=
≠ 90
)
P,
C
,
I
,
F
5.
Hexagonal (
a=
b≠c
and
a
=
b
=
=90
)
P,
C, I, F
6.
Tetragonal(
a=
b≠c
and
a
=
b
=90
=120
)
P
,
C
,
I,
F
7.
Cubic
(
a=b=c
and
a
=
b
=
=90
)
P,
C
, I, F
Seven Systems
Triclinic Body Centered Cell
2
Triclinic
Primitive Cell
1
➢
Triclinic BC
Triclinic Primitive
Seven Systems: Triclinic body-center
Triclinic
(
a ≠ b≠c
and
a
≠
b
≠
≠ 90)
Bravais Lattices
The unit cell which has the smaller number of lattice points
is chosen for the
Bravais list