what is crystallography? the science that examines the arrangement of atoms in solids....
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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
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(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)
Copper sulfate
William Henry Bragg and William Lawrence Bragg (born SA!) derived a formula which describes how crystals diffract (1912). Joint Nobel prize 1915.
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Crystal Diffraction DataCan 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
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Why is Crystallography Important?Earth Sciences – exploration, minerals processing, minerals, high pressure/temperature crystallisation…
Archaeology – paints , residues, ceramics….
Forensic science – soils, powders, paints, explosives, poisons …
Materials science – solar panels,microelectronics, semi-conductors…
Life sciences – DNA, proteins, drugs design…
Metallurgy – phases, hardening, failure, corrosion, heat treatment…
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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 - Crystal Growth
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Demo - Diffraction
n = d Sinθ
Wavelength632.8 nm
‘lattice’ spacinge.g. 2400 lines/inch10,581.6 nm
Diffraction angle, n=1 3.42° n=2 6.87°n=3 10.33
θ
Therefore can work out thickness of hair.Measure angle to regions of destructive interference.Does hair thickness vary between people?
n =1
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Diffraction Facilities
Single crystal system for analysis of the structure of a single phase
Most common form of sample for phase identification and quantification. Microdiffractomet
er - spatial resolution (0.001 mm)
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Crystallography Now –
SynchrotronsWe have one in Melbourne! 216 m in diameter. (also neutrons and electrons)