What is Crystallography?

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What is
Crystallography?
The science that
examines the
arrangement of atoms in
solids.
"crystallography" derives
from the Greek words
crystallon "cold drop,
frozen drop"
What is a crystal? crystalline if the atoms or
ions that compose it are
arranged in a regular way
(Brief) History of Crystallography
Johannes Kepler hypothesized (1611) that the hexagonal
symmetry of snowflake crystals was due to a regular
packing of spherical water particles.
X-rays were discovered by Wilhelm Conrad
Röntgen (1895) Nobel prize in physics in
1901
Max von Laue proposed that a crystal would
act in a similar manner to a diffraction
grating (1912)
William Henry Bragg and
William Lawrence Bragg (born
SA!) derived a formula which
describes how crystals diffract
(1912). Joint Nobel prize 1915.
Copper
sulfate
Crystal Diffraction Data
Can be measured in different ways but one of the most common is as
powders. Each structure gives a unique diffraction data set of peak
intensities and spacings.
Diamond
Graphite
Why is Crystallography Important?
Earth Sciences – exploration, minerals processing,
minerals, high pressure/temperature crystallisation…
Archaeology – paints ,
residues, ceramics….
Materials science – solar panels,
microelectronics,
semi-conductors…
Life sciences – DNA,
proteins, drugs
design…
Forensic science – soils, powders,
paints, explosives, poisons …
Metallurgy –
phases,
hardening, failure,
corrosion, heat
treatment…
Demo - Crystal Growth
Supersaturation drives crystal growth.
Supersaturation is a measure of how much greater the solution
concentration is than at equilibrium.
Can change supersaturation by changing:
 Concentration (add less or let solution evaporate slowly);
 Temperature – supersaturation increases on decreasing temperature.
Blue crystals: CuSO4.5H2O
Solubility 32 g/100 ml H2O at 20 °C.
To make crystals, add 25 g solid into 50 ml water, heat and stir the solution. These
crystals are very easy to grow and started growing within 2-3 hours after the solution
cooling down.
Brown crystals: Fe(NO3)3.9H2O
Solubility 138 g/100 ml H2O at 20°C .
To make crystals, add 70 g solid into 40 ml water, heat and stir the solution. This one
took more than 1.5 day to have crystals grow on the string.
Green crystals: NiCl2.6H2O
Solubility 254 g/100 ml H2O at 20°C.
To make crystals, add 75 g solid into 25 ml water, heat and stir the solution. Took
around one day to have crystals on the string.
Demo - Diffraction
n = d Sinθ
Wavelength
632.8 nm
Diffraction angle,
n=1 3.42°
n=2 6.87°
n=3 10.33
‘lattice’
spacing
e.g. 2400 lines/inch
10,581.6 nm
Therefore can work out thickness of hair.
Measure angle to regions of destructive interference.
Does hair thickness vary between people?
n =1
θ
Diffraction Facilities
Most common form of sample
for phase identification and
quantification.
Microdiffractometer spatial resolution
(0.001 mm)
Single crystal system for
analysis of the structure of a
single phase
Crystallography
Now –
Synchrotrons
We have one in Melbourne! 216 m in
diameter. (also neutrons and electrons)
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