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X-Ray Experiment Presenter: Xu Luo Dec 16, 2009

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Part 1. Introduction Powder method A monochromatic X-ray beam scatters off the randomly oriented powder crystallites, giving rise to diffraction peaks at detector angle 2θ, that satisfy the Bragg’s Law:

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Laue Method(Back Reflection) Reciprocal Lattice and Ewald Sphere Note: A given reflection will only diffract if its reciprocal lattice point intersects the Ewald sphere

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2. Two kinds of explanation of the Back reflection Laue Method A continuous band of X-rays is used to produce diffraction spots on a 2D film where the incident and scattered wave direction satisfy:

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Part 2. Experiment Setup Planes of a zone produce loci of points on film that are either hyperbolae or straight lines.

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Part 3. Analysis 1. The Greninger Chart

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2. Stereographic projection and Wulff net

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3. Determination of the zone axis for a Laue picture hyperbola

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Part 4. Results 1. In our experiment, we found two zone axis poles on the Wulff net. The γ and δ value of them are given below: zone axis 1:, zone axis 2:,

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2. By comparing the zone axis points with several standard projections. We noticed that when rotating the Wulff net over the [110] standard projection, the zone axis points coincide with the points and. Conclusion : The A-B axis (the direction of the X-ray) is [110],and the two zone axis’s we found are : ( on Wulff net); ( on Wulff net)

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Thanks!

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