This document discusses the structure of materials and crystallography. It describes different levels of structure like microscopic, sub-structure, and crystal structure. It also classifies materials based on their chemical makeup, atomic arrangement, and application. Key crystal structures discussed include simple cubic, body centered cubic, face centered cubic, and hexagonal close packed. The document defines concepts like unit cell, lattice points, coordination number, and atomic packing factor. It provides formulas to calculate atomic radius and number of atoms in unit cells for different crystal structures.

1. -CRYSTALLOGRAPHY
(ME010 304)
BY
Asst.Prof. ABHILASH KK

2. MATERIAL SCIENCE
 Study of materials is basically a study
of structure and properties of
engineering materials and on
investigation of structure-property
relationship
 Structure-the arrangement of internal
components of matter in a material
 Property- response of material when
exposed to an external stimulus
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3. LEVEL OF STRUCTURE
 MACRO SCOPIC: Substance visible to
naked eye
 MICROSCOPIC: Structure obtained
under optical microscope.magnification
upto 1500 times linear
 Sub structure: refers to the structure as
obtained using a microscope
 Crystal structure: showing arrangement
of atoms with in the materials. The main
technique employed for determining the
crystal structure is X-ray diffraction
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4.  Electronic structure: it refers to
arrangement of electrons in outer
orbital of individual atoms in a solid
material. spectroscopic technique are
used in determining electron structure
 Nuclear structure: provides the details
regarding constituents with in the
nucleus of atoms in the material.
nuclear magnetic response and
mossbaur studies are the usual
technique used
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5. CLASSIFICATION OF
MATERIALS
 Classification based on chemical
make –up
 Classification based on arrangement
of atoms
 Classification based on application
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6. Classification based on chemical
make up
 Metals-metals are the elements with 1,2,3
valance electrons in outer shells. engineering
materials are either metals or its alloys
Ferrous & non-ferrous
 Ceramics-ceramics are in organic
components between metallic and non –
metallic elements.these includes oxides
,carbides,nitrides,borides,cilicates etc.of
various metals. Example- glasses, clay..etc
 Polymers-organic compounds based on
carbon ,hydrogen and other non-metalic
elements .They are either natural material or
synthetically processed materials like
plastics,phenol ..etc
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7.  Composites- composites are
combination of other above three
categories to produce best , high
quality engineering materials.
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8. Classification based on
arrangement of atoms in a
material  Crystalline material-in which atoms are
arranged in regular, repetitive manner
having long range order. Example-materials
and some ceramics
 Amorphous materials: in which atomic
arrangement does not have any order of
atoms
Example-ceramics and a few polymers
 Molecular materials: grouping of atoms
in short range order exists.
Example- most of the polymers
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9. asst.prof. ABHILASH KK 9

10. Based on application
 Structural materials-no moving
parts(eg.-dams,buildings)
 Materials for machines-moving
parts(automobile)
 Materials for devices-materials for
small parts of devices like measuring
instruments
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11. Bonding force
 Consider two atoms which are
separated by a small distance ,then we
can see that force between atoms is very
high
 force can be classified in to two-attractive
force (fa),repulsive force(fr)
 Net force fn= fa+fr
 At the point where net force equal to
zero is known as point of equilibrium
where fa and fr balance each other
 Here the distance between centers of
two atoms(equilibrium state) is known as
bond length ,denoted as r0
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12.  Where ‘E0’ is the minimum energy required
separate two atoms in an infinite position.
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13. CRYSTAL STRUCTURE
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14. HCP
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15.  . SPACE LATTICE:-space lattice is
defined as an array of points in three
dimensions in which every point has
identical to that every other points in the
array
 UNIT CELL:-The tiny block formed by
arrangement of small group of atoms is
called a unit cell. The unit cell is the
smallest component of the space lattice
 LATTICE POINT:-if Each atoms in lattice
is replaced by a point, then each point is
called lattice point
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16.  Co-ordination number:-it is defined as
the number of nearest atoms which
are directly surrounding a given atoms
 SIMPLE CUBIC STRUCTURE:-6
 BODY CENTERED CUBIC-8
 FACE CENTERED CUBIC-12
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17. TOTAL NO.OF ATOMS IN A
UNIT CELL
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18.  FOR SIMPLE CUBIC STRUCTURE-asst.
prof. ABHILASH KK 18

19. ATOMIC RADIUS
 ATOMIC RADIUS:-defined as the
distance between nearest neighbours in
a crystal of a pure element
 Simple Cubic Structure:-In this structure,
atoms touch each other along the
lattice, as shown in Fig.
 a = 2r
 or r = a/2
 SC
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20.  BCC
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21. asst.prof. ABHILASH KK 21

22.  FCC
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23. ATOMIC PACKING
FACTOR(APF)
 Atomic packing factor(APF)-defined as
the fraction of volume occupied by the
atoms in a unit cell, compared to the
total available volume of the unit cell.
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