Matter, Amorphous & Crystalline, Crystallography, CRYSTAL SYSTEM, Bravais Lattices, CRYSTAL SYMMETRY, Co-Ordination Number, Miller Indices, Crystal imperfection, Liquid crystal

1. CRYSTAL GEOMETRY
AND STRUCTURE
SHEIKH SHAHADAT ISLAM SHAKIL
17ACE019
DEPARTMENT OF APPLIED CHEMISTRY AND CHEMICAL ENGINEERING

2. Matter
 Entity that occupies Space and Volume.
Matter
Solid Liquid Gas Plasma Bose Einstein
condensate
Amorphous
Crystalline
A combination of
both
Metallic Crystal
Non Metallic Crystal

3. Amorphous & Crystalline

4. Metallic & Non Metallic Crystal

5. Crystallography
The Science that examines the arrangement of atom in solid
The terms associated with Crystallography are,
1.Crystal: A 3D periodic arrangement of Atoms in space.
2.Space Lattice: A 3D periodic arrangement of Points in space.
3.Motif / Basis: An atom or Group of atoms associated with each lattice point is called motif
of a crystal.

6. 4.Lattice Translation: Any vector to one Lattice point to another
lattice point.
5.Unit cell: A region of space which can generate the entire
lattice/crystal by repetition through lattice translation.
6.Crystallographic planes: The layers of atoms or planes along
which the atoms are arranged.
7.Lattice Parameter: The length of three edges of unit cell and
the three inter axial angles between them
8.Miller Indices: System of notation for designating
crystallographic planes and direction

7. CRYSTAL SYSTEM
A scheme by which Crystal Structure are classified according to unit cell geometry.
This geometry is specified in terms of the relationship between edge length and inter-axial angles.
The seven different
crystal systems are ,

8. Bravais Lattices
Bravais Lattice refers to the 14 different 3-dimensional configurations into which atoms can be
arranged in crystals.
14 types of Bravais lattices are described with crystal system,
1.Cubic system: In Bravais lattices with cubic systems, the following relationships can be
observed. a = b = c 𝛂 = 𝞫 = 𝝲 = 90o
These three possible cubic Bravais lattices are –
 Primitive (or Simple) Cubic Cell (Polonium)
 Body-Centered Cubic Cell (Iron)
 Face-Centered Cubic Cell (Copper)

9. 2. Orthorhombic Systems
In Bravais lattices with orthorhombic systems the following relations are observed:
a ≠ b ≠ c 𝛂 = 𝞫 = 𝝲 = 90o
The four types of orthorhombic systems are
 simple Orthorhombic (Rhombic Sulphur)
 End/base centered Orthorhombic (Magnesium sulfate hepta-hydrate (MgSO4.7H2O)
 face-centered Orthorhombic (Potassium Nitrate)
 body-centered orthorhombic (barium sulfate)

10. 3. Tetragonal Systems
In Bravais lattices with tetragonal system, the following relations are observed:
a = b ≠ c 𝛂 = 𝞫 = 𝝲 = 90o
The two types of tetragonal systems are,
 simple tetragonal (stannic oxide)
 body-centered tetragonal (titanium dioxide)
4. Monoclinic Systems
In Bravais lattices with monoclinic systems obey the following relations:
a ≠ b ≠ c 𝞫 = 𝝲 = 90o and 𝛂 ≠ 90o
The two possible types of monoclinic systems are,
 primitive or Simple monoclinic (Monoclinic Sulphur)
 End/ base centered monoclinic (sodium sulfate
deca-hydrate)

11. 5. Triclinic System
There exists only one type of triclinic Bravais lattice, which is a
primitive/simple triclinic. (potassium dichromate)
It obeys the following relationship.
a ≠ b ≠ c 𝛂 ≠ 𝞫 ≠ 𝝲 ≠ 90o
6. Rhombohedral System
Only the primitive/Simple unit cell (Calcite and sodium nitrate)
for a rhombohedral system exists. Its cell relation is given by:
a = b = c 𝛂 = 𝞫 = 𝝲 ≠ 90o

12. 7. Hexagonal System
The only type of hexagonal Bravais lattice is the
simple hexagonal cell (Zinc oxide and beryllium oxide)
It has the following relations between cell sides and angles.
a = b ≠ c 𝛂 = 𝞫 = 90o and 𝝲 = 120o

13. CRYSTAL SYMMETRY
Definite ordered arrangement of atom in a crystal is known as crystal symmetry.
Various types of symmetry:
A center of Symmetry An Axis of Symmetry A plane of symmetry

14. Co-Ordination Number
The nearest neighbor to an atom in a crystal.
Simple Cubic B.C.C F.C.C H.C.P

15. Miller Indices
Miller indices, group of three numbers that indicates the
orientation of a plane and Direction of atoms in a crystal.
Miller Indices For Direction:
1.Choose a point on the direction as the origin.
2. Choose a co-ordinate system with axis parallel to unit cell
edges.
3.Find the co ordinate of another point on the direction in
the terms of a, b, c
4.Reduce the Co-ordinates into smaller integers
5.Put it in square bracket
Ex- [1,0,0]

16. Miller Indices For Plane:
1.Select a crystallographic co ordinate system with origin not on
plane.
2.Find the intercepts along axis in terms of respective lattice
parameter.
3.Take reciprocal .
4.Convert to smallest integers in the same ratio.
5.Enclose in parenthesis.
Ex- (1,1,1)

17. Crystal imperfection
Crystal Imperfections are the defects in the regular geometrical arrangement of the atoms in a
Crystalline solid.
 The defects may be the results of the crystal deformation or rapid cooling from high
temperature or high energy radiation striking the solid.
 The defects influence the mechanical, electrical, and optical behavior of the crystal.
The imperfections may be classified widely as:
 Point Defects
 Line Defects
 Planer, Surface, interfacial or grain boundary Defects
 Volume Defects

18. Point Defects

19. Line Defects

20. Surface Defects
Volume Defects

21.  Flow and fracture
 Crystal growth
 Electrical properties (including semi conductor)
 Creep characteristics
 Oxidation and corrosion
 yield strength, fracture strength, plasticity, dielectric strength
Effect of imperfections on Metal

22. Liquid crystal
Liquid crystals are a state of matter which has properties between those of
conventional liquids and those of solid crystals.
For instance, a liquid crystal may flow like a liquid, but its molecules may be
oriented in a crystal-like way.

23. THANK YOU ……..