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<p><img src="https://s1.postimg.org/gcdhagxlr/Diffusion_rayleigh_et_diffraction_svg.svg.png" width="811" height="265"/></p>
<p>Image source: [1]</p>
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<p>In this post I will talk a little about the X-ray diffraction, which allow to determine precisely the parameters of the unit cell; The spatial group containing the information about the crystalline system, the type of network and, in general, the elements of symmetry present in the crystal</p>
<p>The diffractograms are obtained using X-ray radiation with wavelengths shorter than 10 Å, with the different diffractions of each atom constituting the material being recorded. The diffractograms are determined in the reciprocal network, so it is necessary to perform a Fourier transform, in order to move from the real space to the reciprocal space, observing the diffraction process.</p>
<p>more details: [2]</p>
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<p>Introduction of X-rays</p>
<p><img src="https://s7.postimg.org/xl1r41anf/esquema-difraccion-en.jpg" width="409" height="164"/></p>
<p>Image source: [3]</p>
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<p>In 1914, Von Laue first used the x-ray diffraction method to analyze the crystalline structure of materials. According to his theory, atoms of a crystalline structure produce monochromatic and parallel x-ray diffraction; These in turn originate a series of diffracted rays with directions and intensities that depends on the structure and chemical composition of the crystal.</p>
<p>Bragg Law</p>
<p><img src="https://s1.postimg.org/50unykva7/Bragglaw.gif" width="431" height="205"/></p>
<p>Image source: [4]</p>
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<p>It is related to the reflection of the beams incident by the different planes of the glass. The diffraction peaks will be observed only in the directions and wavelengths at which the x-rays scattered from all points of the network interfere constructively.</p>
<p>more details: [5]</p>
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<p>Powder method</p>
<p>To record patterns of diffraction of polycrystalline samples, the powder diffractometer is most commonly used. The design of this instrument allows to replace the electronic photographic register thus providing a high precision in the determination of the positions and intensities of the diffraction maxima.</p>
<p><img src="https://s10.postimg.org/4y2k3xirt/D8-_Discover-bruker.jpg" width="475" height="600"/></p>
<p>Image source: [6]</p>
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<p>Sources: </p>
<p>[1] wikipedia: <a href="https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Diffusion_rayleigh_et_diffract%20ion_svg.svg/811px-Diffusion_rayleigh_et_diffraction_svg.svg.png">https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Diffusion_rayleigh_et_diffract ion_svg.svg/811px-Diffusion_rayleigh_et_diffraction_svg.svg.png</a> </p>
<p>[2] <a href="https://en.wikipedia.org/wiki/X-ray_crystallography">https://en.wikipedia.org/wiki/X-ray_crystallography</a> </p>
<p>[3] google: <a href="http://www.xtal.iqfr.csic.es/Cristalografia/archivos_02/esquema-difraccion-en.jpg">http://www.xtal.iqfr.csic.es/Cristalografia/archivos_02/esquema-difraccion-en.jpg</a> </p>
<p>[4] google: <a href="http://hyperphysics.phy-astr.gsu.edu/hbasees/quantum/imgqua/bragglaw.gif">http://hyperphysics.phy-astr.gsu.edu/hbasees/quantum/imgqua/bragglaw.gif</a> </p>
<p>[5] <a href="https://en.wikipedia.org/wiki/Bragg%27s_law">https://en.wikipedia.org/wiki/Bragg%27s_law</a></p>
<p>[6] serc.carleton: <a href="http://serc.carleton.edu/research_education/geochemsheets/techniques/XRD.html">http://serc.carleton.edu/research_education/geochemsheets/techniques/XRD.html</a> </p>
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<p><img src="https://s4.postimg.org/h9sxo6s5p/voto.gif" width="1277" height="240"/></p>
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