2. What is X-ray diffraction?
non-destructive analytical
technique for identification
and quantitative
determination of the various
crystalline forms, known as
‘phases’.
Identification is achieved
by comparing the X-ray
diffraction pattern
3. What is X-ray diffraction?
Crystalline substances (e.g. minerals) consist of
parallel rows of atoms separated by a ‘unique’ distance
Diffraction occurs when radiation enters a crystalline
substance and is scattered
Direction and intensity of diffraction depends on
orientation of crystal lattice with radiation
4. History of X-Ray Diffraction
1895 X-rays discovered by
Roentgen
1914 First diffraction pattern of a
crystal made by Knipping
and von Laue
1915 Theory to determine crystal
structure from diffraction
pattern developed by
Bragg.
1953 DNA structure solved by
Watson and Crick
Now Diffraction improved by
computer technology;
methods used to determine
atomic structures and in
medical applications
5. Basic Components Of XRD Machine
Monochromatic X-ray
source ()
Sample-finely powdered
or polished surface-may
be rotated against the
center – (goniometer).
Data collector- such as
film, strip chart or
magnetic
medium/storage.
6. How Diffraction Works?
Wave Interacting with a Single Particle
Incident beams scattered uniformly in all directions
Wave Interacting with a Solid
Scattered beams interfere constructively in some
directions, producing diffracted beams
Random arrangements cause beams to randomly
interfere and no distinctive pattern is produced
Crystalline Material
Regular pattern of crystalline atoms produces
regular diffraction pattern.
Diffraction pattern gives information on crystal
structure
9. Crystal Lattice
A crystal lattice is a regular three dimension
distribution (cubic, tetragonal, etc.) of atoms in
space. These are arrange so that they form a
series of parallel planes separated from one
another by a distance d, which varies according
to the nature of the material. For any crystal
planes exist in a number of different
orientations- each with its own specific d-
spacing
10. Factors that affect XRD data
Sample not powdered fine enough
May not give all d-spacing data (not random
enough)
Analysis too fast (degrees/minute)
May not give accurate peak data
Mixture of minerals??
Not crystalline – glass!!
11. Applications of X-Ray Diffraction
Find structure to determine function of
proteins
Convenient three letter acronym: XRD
Distinguish between different crystal
structures with identical compositions
Study crystal deformation and stress
properties
Study of rapid biological and chemical
processes
Crystallographic applications
12. X-ray diffraction is important for:
Solid-state physics
Biophysics
Medical physics
Chemistry and Biochemistry