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Title: PHYSICAL CHEMISTRY
Description: The latest updated notes on physical chemistry
Description: The latest updated notes on physical chemistry
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SCH 409: Structural Chemistry
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
1 / 36
Presentation Outline
1
Crystal Structure
2
Departure From Perfect Crystal
3
CRYSTALLOGRAPHY
Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
3 / 36
Gases
Particles are very far
apart
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
4 / 36
Gases
Particles are very far
apart
Particles move very
fast
No definite shape and
No definite volume
Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
5 / 36
Liquid
Particles are spread
apart
Particles move slowly
through a container
Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
5 / 36
Liquid
Particles are spread
apart
Particles move slowly
through a container
No definite shape but
do have a definite
volume
Flow from one
container to another
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
6 / 36
Solid
Particles are tightly packed and close together
Particles do move but not very much
Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
6 / 36
Solid
Particles are tightly packed and close together
Particles do move but not very much
Definite shape and definite volume (because
particles are packed closely and do not move)
Most solids are crystals
Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
6 / 36
Solid
Particles are tightly packed and close together
Particles do move but not very much
Definite shape and definite volume (because
particles are packed closely and do not move)
Most solids are crystals
Crystals are made of unit cells (repeating
patterns)
The shape of a crystal reflects the
arrangement of the particles within the solid
Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
7 / 36
Objectives
Be able to identify a unit cell in a symmetrical
pattern
Know that (in 3 dimensions) there are 7 (&
ONLY 7!!) → Possible unit cell shapes
...
Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
7 / 36
Objectives
Be able to identify a unit cell in a symmetrical
pattern
Know that (in 3 dimensions) there are 7 (&
ONLY 7!!) → Possible unit cell shapes
...
Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
7 / 36
Elementary Crystallography
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
9 / 36
Crystalline Material
atoms self-organize in a
periodic array
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Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
11 / 36
Single crystal
atoms are in a repeating or
periodic array over the
entire extent of the material
(each atom is related to
every other equivalent atom
in the structure by
translational symmetry)
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
13 / 36
Polycrystalline material
Is made up of an aggregate
of many small single
crystals (crystallites or
grains)
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
14 / 36
Polycrystalline material
Is made up of an aggregate
of many small single
crystals (crystallites or
grains)
...
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Dr
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These regions are called grains
(or domains) & are separated
from one another by grain
boundaries
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
15 / 36
Polycrystalline material
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
17 / 36
Amorphous (Non-crystalline) Solids
lacks a systematic atomic
arrangement
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Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
20 / 36
Presentation Outline
1
Crystal Structure
2
Departure From Perfect Crystal
3
CRYSTALLOGRAPHY
Dr
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They contain impurities, voids,
misplaced atoms and other
defects
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
22 / 36
Departure From Perfect Crystal
Crystals are not perfect
...
crystalline defects are responsible
for many of the useful properties
of materials; a perfect and
perfectly pure crystal is generally
useless
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
22 / 36
Presentation Outline
1
Crystal Structure
2
Departure From Perfect Crystal
3
CRYSTALLOGRAPHY
Dr
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Dr
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Symmetry of a crystal can have a
profound influence on its
properties
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
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Why crystallography is essential
...
Any crystal structure should be
specified completely, concisely
and unambiguously
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
25 / 36
Why crystallography is essential
...
Any crystal structure should be
specified completely, concisely
and unambiguously
...
Dr
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Dr
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Dr
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
29 / 36
Symmetry properties of the lattice
What about translation?
Translations are restricted to only
certain values to get symmetry
(periodicity)
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
31 / 36
This array of points is a LATTICE
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
33 / 36
Not a lattice:
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some kind of STRUCTURE because
not just points
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Kiruri (Kenyatta University)
SCH 409: Structural Chemistry
May 27, 2015
36 / 36
Summary: Lattice structure
An ideal crystal is constructed by
the infinite repetition of identical
groups of atoms
A group is called the basis
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Dr
Title: PHYSICAL CHEMISTRY
Description: The latest updated notes on physical chemistry
Description: The latest updated notes on physical chemistry