14S1-MSE002-Crystal Structure 1.pdf

7/25/2019 14S1-MSE002-Crystal Structure 1.pdf

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CRYSTAL STRUCTURE -1

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www.amiestudy.com

EXCELLENCE ACADEMY

Name: Arun J

Class Name: MSE002 Batch: 14 S1
http://www.amiestudy.com/http://www.amiestudy.com/


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Content

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Type of atomic bonding

Type of crystal lattices

Crystal structures in metallic materials

Methods to specify the directions and planes in

crystalline material

EXCELLENCE ACADEMY MATERIAL SCIENCE AND ENGINEERING


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Atomic bonding3

Materials are composed of atoms.

Each atoms are closely packed in some manner and

exerts forces on each other- attractive or repulsive.

When these forces are equal there exist a state of

equilibrium.

After that the energy required to separate two

atom is called bonding energy. The bonding are ofdifferent types mainly



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Primary bonding4

Ionic bond- Composed of metallic and

nonmetallic elements e.g. Li, Na, K and F, Cl ,

Br. Atoms of metallic element give up their

valence electrons to non metallic atoms andform stable.

This is non directional i.e. magnitude is equal in

all direction (+ve attracts all neighboring ve)

Bad conductor of electricity and temperature

because ions are held tightly.



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Continued5

Covalent bond- The central group of elements in

periodic table are not ready to give their valence

electrons because it is too large. Hence ionic bond is

not possible and so sharing of electrons in outermostshell take place and is called covalent bond.

It is directional because the centers of +ve and ve

charges are dispersed

Bad conductors of electricity and temperature

because outermost electrons are shared.



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Continued6

Metallic bond- Forms due to electrostatic force of

attraction between +ve ions and ve electron cloud of

same or different material.

It is non directional because +ve ion and electron cloud

take part in formation of bond.

These are good conductors of electricity and

temperature because of free electrons.

Secondary bond- Exist between virtually all atoms ormolecules along with primary bond . Usually seen in

elements or compounds where no electron transfer takes

place.



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Crystallography7

Atoms of some materials arrange themselves in

regular systematic pattern in three dimensions

called crystalline materials.

Space lattice- Crystalline material is formed whenatoms arrange in three dimensional pattern, in

which rows can be identified in various directions

along which atoms are regularly placed and the

centers of the atom are connected by straight lines.Then a network of lines are formed called space

lattice or crystal lattice.



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Continued

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Unit cell- In a crystal lattice the repetition of cells whichproduce the crystal can be identified called unit cell i.e.it is the building block of a crystal.

Unit cells for most crystal structures are parallelopipeds

or prism whose inter atomic spaces along three axis is a,b, c and inter axial angles are .

In a unit cell there are definite locations where atomsare positioned and these are called lattice points.

Depending upon the relation between latticeparameters they are classified into seven groups and isagain classified into 14 typed based on atomicarrangement.



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Continued9

Various arrangement includes

Lattice point at cell corners- simple

Lattice point at centre of two opposite faces in addition

to cell corners- base centered

Lattice point at centre of all the faces in addition to

corner.

Lattice point at body centre in addition to corner.



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Crystal system

ONLINE AMIE COACHING MATERIAL SCIENCE AND ENGINEERING

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Continued..

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C i d


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hank you

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References14

IP Singh, Material Science & Engineering ,Jain

Brothers New Delhi

Navneet Gupta, Material Science & Engineering,

Dhanpat Rai & Co New Delhi

Dr.S Jose, Metallurgy and material science ,

Pentagon Education Services , Kerala


14S1-MSE002-Crystal Structure 1.pdf

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