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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.

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Presentation on theme: "What is Crystallography? The science that examines the arrangement of atoms in solids. "crystallography" derives from the Greek words crystallon "cold."— Presentation transcript:

1 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

2 (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.

3 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

4 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: CuSO 4.5H2OSolubility 32 g/100 ml H 2 O 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(NO 3 ) 3.9H 2 OSolubility 138 g/100 ml H 2 O 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: NiCl 2.6H 2 O Solubility 254 g/100 ml H 2 O 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

5 Demo - Diffraction n = 2d Sinθ Wavelength nm ‘ lattice’ spacing e.g lines/inch 10,581.6 nm Diffraction angle, n=1 0.85° n=2 1.71° n= θ2θ Therefore can work out thickness of hair. Measure angle to regions of destructive interference. Does hair thickness vary between people?

6 Diffraction Facilities Single crystal system for analysis of the structure of a single phase Most common form of sample for phase identification and quantification. Microdiffractometer - spatial resolution (0.001 mm)

7 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…

8 Crystallography Now – Synchrotrons We have one in Melbourne! 216 m in diameter. (also neutrons and electrons)


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