X RAY DIFFREACTION

2. Contents:
•INTRODUTION
•DEFINITION
•PRINCIPLE
•BRAGG’S DIFFRACTION
•X-RAY DIFFRACTION METHODS
•LAUE PHOTOGRAPHIC METHOD
•BRAGG’S X-RAY SPECTROMETER METHOD
•ROTATING CRYSTAL METHOD
•POWDER METHOD
•INSTRUMENTATION
•Source of x-ray
•Sample preparation &holder
•Detector
•Recording &interpretation
•APPLICATION OF CRYSTALS

3. X-RAY DIFFRACTION
INTRODUCTION:
X-Ray crystallography is a methods of
determining the arrangement of atoms within a crystal, in which
a beam of x-ray strikes a crystals and cause the beam of light to
spread into many specific directions from the angles and
intensities of these diffracted beams a crystollograper can
produce a three dimensional picture of the density of the density
of electrons within the crystal
Because x-ray have wavelength similar to the size of
atoms, they are useful to explore within crystals.

4. Definition :
 x-ray crystallography uses the uniformity of light diffraction of crystal to
determine the structure of a molecular or atom
 Then they use an x-ray beam to ‘hit’ the crystalized molecular
 The electrons surrounding the molecular diffraction the x-ray hit them.
 This forms a pettern, this type of pattern is called the x-ray diffraction

5. Pr incipl e:
Br a gg’s dif f r a ct ion:
Diffraction from a three dimensional periodic
structure such as atoms in a crystal is called
bragg’s diffraction
Similar to diffraction through grating
Consequence of interference between waves
reflecing from different crystal planer
X-ray diffraction (bragg’s law )
n𝜆 = 2𝑑 sin 𝜃

7. n𝜆 = 𝐴𝐵 + 𝐵𝐶
AB=BC
Hence, n𝜆 = 2𝐴𝐵 − − − − − 1
Sin 𝜃 =
𝐴𝐵
𝑑
dsin 𝜃 = 𝐴𝐵
2dsin𝜃 = 2𝐴𝐵−−−−−−2
Equcation1&2
n𝜆 = 2𝑑sin𝜃

8. 𝜆=is the wave length of the x-ray
d= is the interplaner spacing in the specimen
𝜃= is the diffraction angle (discussed later)
 The bragg’s equation is the fundamental equation , volid
only for monochromatic x-rays ,that is used to calculate
interplaner specinds used in XRD analysis.

9. x -r a y dif f r a ct ion met hods
 La ue phot ogr a phic met hod
 Br a gg’s x -r a y spect r omet er met hod
 Rot a t ing cr yst a l met hod
 Powder met hod
LAUE PHOTOGRAPHIC MRTHOD
Studied the phenomenon of diffraction of crystal two
method
a) Trasmission method
b) Back reflaction method

10. TRANSMISSION MATHOD
This experimental equipment required for this is
relatively simple.

11. i. A-is a source of x-ray ,
Continuous wave length known as white radiation,
60,000volts
ii. B-is a pinhole collimator.
iii. C-is a crystal whose internal structure is to investigated,
the crystal is set on a holder to adjust its orientation.
iv. D-is a film arranged on a rigid base , this film is provided
with beam stop to prevent fogging of the film

12. BACK –REFLECTION METHOD
 This method provides similar information as the
transmission method
 The back –reflection method is the only method for the
investigation of large and thick specimens
 The main disadvantage of required and further more
there is uncertainly in the significance due to
unhomogeneous nature of x-ray .

13. Rot a t ing cr yst a l met hod

14. a) X-ray are generated in the x-ray tube and then the beam is
made monochromatic by a filter
b) From the filter, the beam is then allowed to pass through
collimating system which permits a fine pencil of parallel
x-ray
a) Collimator,the x-ray beam is made to fall on a crystal
mounted on a shaft which can be rotated at a uniform
angular rate by a small motor.
b) Now the shaft is moved to put the crystal it slow rotation
about a fixed axis .
c) This causes the sets of planes coming successively reflecting
position
One can take photography in two ways;
 Complete rotation method
There occurs a series of complete revolution
 Oscillation method
Crystal is oscillated through an angle of 150

15. Powder cr yst a l met hod
 In all the above described method ,a single crystal
is required whose size is much larger then
microscopic dimensions.
 The powder method , the crystal sample need not
be taken in large quantity but as little as 1mg of
material is sufficient for the study.
 The experimental arrangement of powder crystal
method
i. A is a source of x-ray which can be made
monochromatic by a filter
ii. Allow the x-ray beam to fall on the powdered specimen
P through the slits S1 &S2

16. i. Fine powder, P struck on a hair by means of gum is
suspended camera.
This enable sharp lines to be obtioned on the
photographic film crystal in the from of a circular arc.
ii. X-ray after falling on the powder passes out of a the
powder passes out of the camera through a cut in the
film so as to minimize the fogging produced by the
scattering of the direct beam
iii. On a flat photographic plate the observed pattern
consists of traces

18. Application of crystals:
I. STRUCTURES OF CRYSTAL
 This analytical application of x-ray diffraction are numerous
 The method is nondestrative and gives information on the molecular structure of
the sample.
 Most important use has been to measure the size of crystal planes
 Eg, kcl &Nacl
POLYMER CHARACTERISSATIONS:
Powder method can be used to determine the
degree of crystallinity of the polymer.
The non-crystalline portion simply scatters the x-
ray beam to give a continuous background while
the crystalline portion cause diffraction lines that
not continuous

19. STATE OF ANNEAL IN METALS.
Well -annealed metals are in well –orderd crystal from and
give sharp diffraction lines
PARTICLE SIZE DETERMINATION:
X-ray techniques may be used to determine
the size particles or crystallities
Spot counting method
 𝑣 = 𝑉. 𝛿𝜃.
𝐶𝑂𝑆𝜃
2𝑛
Broadening of diffraction lines
 Range 30-1000A0
LOW-ANGLE SCATTING
 Have the already of spot counting and
broadening of diffraction lines method
 Both these method give a mean crystallite
dimension and distibution of particle size.

20. APPLICATION OF DIFFRACTION MRTHOD COMPLEX
a)DETEMINATION OF CIS-TRANS ISOMERISUM
 Used to make the distinction between cis &
trans isomers of a complex
 Ex , bil/ pyridine (2-carboxamid)nickel.
b) DETERMINATION OF LINKAGE ISOMERSIUM
 X-ray studies, becomes poosible to identify linkage
isomers of complexs.
 Some times knowledge of the possible of hydrogen
atoms is useful

21. PHARMACETICAL APPLICATION :
Measurement of the average space ‘d’ between layers of
atoms
Determination of the orientation of a single crystal and
crystal structure of unknown material
Measurement of size , shape and internal stress of small
crystalline regions
Measurement of thickness of thin films and multi layers
Determination of each type in mixed crystals (up to 3%
in a mixture )
Comparison of XRD pattern with the database of
thousands of compounds for interpertation

22. MEDICINE:
 X-RAY are a good use in the medical field because
it can help doctors figure out what is going on in our
bodies.
 It also help from understand the structure frame
that might damage so, they know what they need to
do in order to repair it
 X-ray let the person being checked also know what
is going on in their bodies and how they can find way
to themselves , health wize.
INDUSTRY:
 X-ray machines are used in airport to check
luggage etc……..
SCIENCE:
 X-ray used to analyse the arrangement of atoms in
many in particulary crystals.