Principle x ray diff
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Transcript of Principle x ray diff
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Principle Of X-Ray Diffraction
PRESENTED BY;
Aiswarya. A.T.,I year M.Pharm.,Dept. of Pharmacy Practice,Grace College of Pharmacy
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X – Ray Diffraction
“ Every crystalline substance gives a pattern; the same substance always gives the same pattern; & in a mixture of substances each produces its pattern independently of the others”
The X-ray diffraction pattern of a pure substance is, therefore, like a fingerprint of the substance. It is based on the scattering of x-rays by crystals.
Definition : The atomic planes of a crystal cause an incident beam of X-rays to interfere with one another as they leave the crystal. The phenomenon is called X-ray diffraction
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Principle
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Bragg’s Law and Diffraction
William Henry Bragg
Diffraction occurs only when Bragg’s Law is satisfied Condition for constructive interference (X-rays 1 & 2) from planes with spacing d
Xray 1Xray 2
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Constructive interference X-ray 2 occurs only when,
n ƛ = AB + BC
AB=BCn ƛ =
2ABSin θ
=AB/dAB=d
sin θn ƛ =2d
sin θ ƛ = 2 d sin θ
AB+BC = multiples of n ƛ
Xray 1
Xray 2
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Measure the average spacing's between layers or rows of atoms
Determine the orientation of a single crystal or grain
Find the crystal structure of an unknown material
Measure the size, shape and internal stress of small crystalline regions
Why XRD???
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Thank U !!!