This document summarizes a seminar on crystal structures presented by Madhusmita Sethy at Dr. Hari Singh Gour Vishwavidyalaya University. It defines crystals as solids composed of atoms or molecules arranged periodically in three dimensions. Crystals are made up of basic building blocks including unit cells that repeat through translation, lattices consisting of periodic arrays of points, and motifs or basis of one or more atoms located in a specific way. The document outlines six major crystal systems and discusses crystal structures, Pauling's rules of crystal chemistry, polymorphism, and the significance of understanding crystal structures.

1. DR. HARI SINGH GOUR VISHWAVIDYALAYA
SAGAR,M.P.
(A CENTRAL UNIVERSITY)
SEMINAR ON – CRYSTAL STRUCTURE
UNDER SUPERVISION OF
PROF. R.K. TRIVEDI PRESENTED BY-
MADHUSMITA SETHY
REG- Y18251015
1ST SEMESTER

2. CONTENTS
 INTRODUCTION
 UNIT CELL
 LATTICE
 BASIS
 CRYSTAL STRUCTURE
 CRYSTAL SYSTEM
 X- RAY DIFFERACTION
 PAULINGS RULES
 POLYMORPHISM
 SIGNIFICANCE
 REFERANCE

3. INTRODUCTION
 Crystal are solid composed of atoms, ions, or molecules that
periodic in three dimension.
 It has regular geometry form- physio-chemical condition ,
slow cooling.
 These are polyhedral bodies.
 Crystals are made of small basic building block.
 All crystal system are classified into six major crystal system,
namely Isometric, Tetragonal, Hexagonal, Orthorhombic,
Monoclinic , and Triclinic system.

5. Unit cell
• The basic building block of crystal.
• It repeat itself by translation through the
crystal.
– The most common type of unit cell are
– Face centered cube (FCC)
– Body centered cube (BCC)
– Hexagonal close packing(HCP)

7. LATTICE
• An infinite periodic array of points in a space.
• A lattice may be one,two, or three
dimensional.
• The arrangement of points defines the lattice
symmetry.
• Auguste Bravais demonstrated 3-dimensional
system there are fourteen possible lattice.

8. BRAVAIS LATTICE

9. MOTIFS
A Group of one or more atoms, located in
a particular way with respect to each
other and associated with each point, is
known as the Motifs or basis.

10. CRYSTAL STRUCTURE
• Crystal structure =Crystal lattice + Basis
• So we can say that, When an atom or identical
group of atoms is attached to every lattice
point, we obtain a crystal structure.

11. • Crystals are classified into two types
I. Poly crystal- Periodicity is not maintained
throughout the body.
II. Single crystal- Periodicity is maintained
throughout the body.

12. STRUCTURE OF NaCl

13. METALLIC CRYSTAL STRUCTURE AND
POLYCRYSTALS

14. THE MOST IMPORTANT CRYSTAL
STRUCTURES
• Cesium Chloride structure
• Hexagonal closed packed structure
• Diamond structure
• Zinc Blend

15. DIAMOND
STRUCTURE
ZINC BLENDE
STRUCTURE
HEXAGONAL
CLOSE PACKING
STRUCTURE

17. PAULINGS RULE
• First rule-Radius Ratio Principle
• Second rule-Electrostatic Valency Principle
• Third rule-Sharing polyhedra
• Fourth rule-Small cation with high charge do
not share anion easily with other cation.
• Fifth rule-Principle of parsimony.

21. POLYMORPHISM
• It is the ability of a solid material to exist in
more than one form or crystal structure.
Different type of polymorphism are
 Packing polymorphism
 Conformational polymorphism
 Pseudo polymorphism

22. SIGNIFICANCE OF CRYSTAL STRUCTURE
• Difference between two mineral.
• It has a great importance in Biology.
• It also helpful determining the element in a
mineral.
• It tells about the bonding between atoms.

23. Reference
• Askeland R. Donald, The science and
engineering of materials, Publisher : Bill
Stenquist, fourth edition
• Nesse D. William, Introduction to Mineralogy,
Publication: Oxford University Press, 2nd
edition
• Perkins Dexter, Mineralogy, Publication:
Pearson, 3rd edition
• Google images