X-ray diffraction methods are used to study the structure of solids. When X-rays interact with the periodic crystalline structure of a solid, they produce a specific pattern of diffracted beams. By analyzing these diffraction patterns using Bragg's law, properties of the crystal such as lattice parameters and unit cell dimensions can be determined. There are several techniques for X-ray diffraction including single crystal diffraction, powder diffraction, and rotating crystal diffraction. These techniques provide information about atomic and molecular structures within crystals.

1. X –RAY DIFFRACTION METHODS
Presented by:-KANIKA
(B.Pharmacy8th sem.)
LORD SHIVA COLLEGE OF PHARMACY,SIRSA

2. INTRODUCTION
X-ray is electromagnetic radiation
wavelength=0.01nm to 10nm OR 0.1A0 to 100A0
ENERGY=100eV to 100keV
A variety of X-ray techniques and methods are in use. But
we shall classify all methods in main 3 categories:-
X-ray absorption method
X-ray diffraction method
X-ray fluorescence method

3. X-ray absorption method:- A beam of x-rays is allowed to pass
through the sample and fractions of X-ray photons absorbed is considered to be
a measure of concentration of absorbing substance.
Only helpful in elemental analysis and thickness measurements.
X-ray diffraction methods:-
It is for study the structure of solids with high degree of specificity..and
based on scattering of X-rays by crystals . This is extremely important and
by careful analysis of diffraction patterns , very accurate values of lattice
parameters(unit cell dimensions) can be inferred.
X-ray fluorescence method:-
Non destructive and requires very little sample for analysis and also perform
qualitative and quantitative analysis , when atoms will excite from G.s to
excited stated then from E.s coming back to G.s it inhibit some radiation
and those radiation have longer wavelength then actual one called
fluorescence.

4. ORIGIN OF X-RAYS:- Invented by a German physicist Wilhelm
Roentgen(in 1895).
1. X-rays are generated can be described by using Bohr’s theory of atomic
structure .When high velocity electrons will strike the metal target and
electron will knockout from target atom and due to lose of energy X-ray will
produce.

5. 2. It also can be produced when high velocity electrons strike the Anode
material in discharge tube(x-ray tube) . Velocity of electrons will decreased and
that will radiate protons and responsible for x-ray production.
3.By the decay of certain radioactive isotopes.
EXPLAINATION:-
1.When high velocity electrons are strike on metal target and produce x-
ray that can be describe by using Bohr’s theory of atomic str.
like in fig. and energy of outer
cell
will Higher as compared To inner
cell. Now ,if 1 electron of high
velocity will destroy the atom
then it will knock out 1 electron
from atom .Thus , VOID will
produce .

6. Therefore , to fill this void space electron may come from there
N/L/M shells so electron come from higher energy to lower
energy level so that will release some energy and that energy will
release x-rays. This released x-ray energy will be equal to
difference in the energy between 2 shells . If electron vacant sites
filled by L shell , then
{ X-ray energy = L(cell energy)-K(cell energy) }
E x-ray =EL-EK(if electron fall from L-shell),EM-EK(if fall
from M-shell) and so on….so frequency of emitted X-
rays will be , v=
(v=velocity)
(h=Planck’s constant)
h
EK
EL

7. By using this , X-RAY pattern of any target is:-
A primary use of technique is the identification
and characterization of compounds based on
their diffraction pattern. The diffraction of X-rays
by crystals is described by BRAGG’S LAW(will
discuss in next slide)

8. (V= X-ray tube voltage)
max.= min.*1.5
eV
hc
V
12400
V
1240

9. 2.High velocity electrons strike the anode material in discharge
tube for release x-rays…….
After striking of electron on anode
then go around nucleus of target
material where proton and neutrons
present so will produce High
electric field thus , velocity of that
electrons will decreased energy and
will radiate and produce X-rays OR
we can also say that , deceleration of
striking electrons and electrons will
loss its kinetic energy that will
radiate protons so will release of
energy.
The process by which photos are
emitted by an electron known as
BREMSSTRAHLUNG.

10. Initial Energy of striking electrons : Ei
Energy for X-ray : Ex-ray
Final energy of electrons after deceleration: E f
Thus, E f =E i-Ex-ray
Ei =Ef +Ex-ray
Due to heavy mass of nucleus as compared to electrons , Nucleus
will absorb very less energy in order to consume linear
momentum.
If all initial kinetic energy (Ei) will convert into X-rays then
velocity of electrons become Zero; Ef =0
Ei=Exray
Therefore , in this condition it will give X-rays of highest energy
or lowest wavelength.

11. BRAGG’S LAW
The diffraction of X-rays technique used for structural determination of
any crystalline structure by that is described by this law-
n=2dsin

12. The directions of possible diffractions depend on size and shape
of unit cell of the material . The intensities of diffracted waves
depend on kind and arrangement of atoms in the crystal structure
. However , most materials are not single crystals , but are
composed of many crystallites in all possible orientations called a
polycrystalline aggregate or powder.
BASIC ASPECTS OF CRYSTALS:-
CRYSTAL= Any solid material in which component atoms are
arranged in definite pattern and whose surface regularly
reflects its internal symmetry[also defined as Regular
Polyhedral form]
Classified into 2 types:-(1) Poly crystal(2)Single crystal

13. CRYSTALLOGRAPHY:-Experimental Sci. of arrangement of
atoms in solids . Greek words ,(CRYSTALLON)->cold drop/frozen drop
its meaning extending to all solids with some degree of transparency and
(GRAPHO)->write.

14. BASIC (Motif):- [Crystal str.=Lattice + Basis]
Lattice:-3-DTranslationally periodically arrangement of points.
Basis:-A group of 1 or more atoms , located in particular way w .r . t each
other and associated with each point . So , we can say that when an atom or
identical group of atoms is attached to every lattice point we obtain a crystal
structure.
Many crystals are described as solids with long range/3-D
internal order . Each unique piece of 3-D array is called a
unit cell.

15. Shape of any unit cell is described by 3 VECTORS : a , b , c
These vectors lead to 6 parameters the 3 cell lengths:-a/b/c and 3 inter axial
angles:-//
 X-RAY are scattered from different atoms in sample and interfere
with one another either constructively or destructively.
 For crystalline solids this interference pattern has sharp well
defined peaks , the position of peaks are determined by
LATTICE for crystalline solid.

16. Fig. INTERFERENCE PATTERN
OF PEAKS
X-RAY
CRYSTALLOGRAPHY:- > Technique used for determining the atomic
and molecular structure of a crystal.
>Principle :-The crystalline atoms cause a beam of X-rays to diffract into many
specific directions.[SCATTERING AND DIFFRACTION]
>By measuring the angles and intensities of these diffracted beams ,a
crystallographer can produce a 3D Picture of density of electrons within the
crystal.
>From this electron density image , the mean positions of atoms in crystal can
be determined , as well as their chemical bonds , their disorder and various
other information can also be determined.
>The method revealed the structure and function of many biological molecules
including:-Vitamins , drugs , proteins and nucleic acids such as DNA.

17. >Note:- Double helix structure of DNA discovered by James Watson and
Francis Crick was revealed by X-ray crystallography.
>Recent advances in image reconstruction technology have made X-ray
crystallography amenable to structural analysis of much larger complexes such
as; VIRUS Particles.
INSTRUMENTATION:-
1. SOURCE
2. COLLIMATOR
3. WAVELENGTH SELECTOR
4. SAMPLE HOLDER
5. DETECTOR
6. RECORDER
1.SOURCE:- Production of X-rays using :[I]X-ray tube(Coolidge Tube)
[II]Radioisotopes
[I]x-ray tube consists of an evacuated tube made up of glass fitted with
Tungsten filament(at one end of tube called{cathode} and heated
by using a High Voltage & metal target at other end called{anode}
that is heavy block of copper coated with target material which
emits X-ray.

18. >cold water can be circulated in some areas to
avoid excess heat.
>Electrical current is run through Tungsten
filament , causing it to glow and emit
electrons.
>A large voltage difference is placed between
the cathode and the anode, causing the
electrons to move at high velocity from
filament to anode target.
>working as (2nd origin of x-rays)
 >>High the voltage applied-greater
 electrons emitted out-High
 intensity of X-ray.
 >>Great accelerating force-High energy of
x-rays-Shorter wavelength.
Adv.:-produce Continuous spectrum of X-rays .
Lim.:-unnecessary heating of anode ; poor output efficiency.

19. [II]Certain radioactive substances produces X-ray as a result of
their radioactive decay process and can act as source of X-ray .
Elements like 26Fe55/27Co57/48Cd109 produce x-rays by electron
capture.
2.COLLIMATOR:- x-ray produced by target material is randomly
directed. This consist of 2 sets of closely packed metal plates
separated by small gap. This absorbs all X-rays except the narrow
beam that passes between the gap.
3.WAVELENGTH
SELECTOR:-
Isolation of
monochromatic
x- rays can be
achieved by
[I]FILTERS
[II]MONO-
CHROMATORS.

20. .
[I] X-ray Photometers used .
Filters are of
specific material ;
different thickness ;
thin metallic strips
(from target material x-rays allowed to
pass through thin strip(0.01 cm
thickness).
>It also produce 2 lines K and K .
>Example:-Zirconium filter is used for
molybdenum radiation
[II] Crystal monochromator used.
>Made up of suitable crystalline
material(NaCl /LiF/Quartz etc.).
>Works on principle of Bragg’s equation.
>Crystal placed on rotating
table/Goniometer
>Beam splits by the crystalline material
into component  in same way as prism
splits white light into rainbow .
>Useful  range from crystal is
determined by lattice spacing(d)
>2 types
-flat crystal mono.
-curved crystal mono.

21. 4.SAMPLE HOLDER:-Rotating table called as a crystal mount . A sample is a crystal is
placed at the centre of crystal mount , which is kept rotating at a particular speed.
5. DETECTOR:- X-ray intensities can be measured and recorded either by:
[I]PHOTOGRAPHIC :-In this , plane or cylindrical film is used . The film exposing to x-ray
is developed and blackening occurs (expressed in terms of density{D})
D=log IO(incident)/I(transmitted intensities of x-rays)
Adv.:-High sensitivity ; Selective method
Lim.:-Time consuming
[II]COUNTER METHODS: > GM Tube counter:-
#Tube is filled with an inert gas (Argon) and central wire(Anode) maintained at +ve
potential(800 to 2500V)
#When x-rays enters the tube , rays undergoes collision with the filling gas , thus produce
an ion pair;electrons produced moves towards the central anode while =ve ion moves
towards outer electrode.
#Electrons is accelerated by potential gradient and causes ionization of large no. of argon
atoms.This results in output pulse of 1 to 10V i.e measued by simple circuit.

22. Adv.:High signal intensity/trouble
free
Lim.:used for counting low
rates/efficiency falls

27. SINGLE CRYSTAL DIFFRACTION:-
>Oldest and most precise .
>Non-destructive analytical technique provide detailed
information like Unit cell dimension ; Bond length ; Bond angle ;
details of Site Ordering, about Internal lattice of crystalline
substances.
Principle:-
Consist of
3 basic elements:-
1.X-ray tube
2.Sample holder
3.Detector
X-ray beam strike on a single crystal
produce scattered beams land on piece
of film/detector
Makes diffraction pattern of spots
Beam’s strength and angle are
recorded as crystal gradually rotated.

28. 1.X-ray generated in cathode ray tube by heating a filament to
produce electrons--After apply voltage, accelerate the electrons
towards target --when electrons have sufficient energy to dislodge
inner shell electrons of target materials(molybdenum)—x-ray
produce spectra(mostly components K and K)
2.Monochromatic x-rays directed into sample—when geometry of
incident x-rays satisfied Bragg’s eq’n—constructive interferences
occurs.
3.Record the x-ray signal and output on computer system.
Advantages
• Only require preparation of minimal
sample.
• Straight forward result
Limitations
• Typically XRD req. to access Std. data
• If crystal sample is non-isometric the
indexing of patterns can be complex to
determine unit cell.

29. POWDER DIFFRACTION:-Only analytical method i.e
capable of furnishing both qualitative and quantitative info about
the compounds present in solid sample.
>In this, crystal sample need not to be taken in large qty.
>Crystalline material contained in capillary tube is placed in
camera(containing film strip)
>sample rotated by means of motor
>X-ray pass through gap between ends of film
>powdered sample contains small crystals arranged in all
orientations(some of these will reflect x-ray from each lattice
plane at same time)
>Reflected x-rays will make an angle 2 with original directions
>hence on diagram –obtained lines of constant 
>from geometry of camera,  can be calculated for different crystal
plane.

31. Adv.:-X-rays are not absorbed very much by air, so specimen need
not to be in an evacuated chamber.
Lim:-They don’t interact very strongly with lighter elements.
ROTATING CRYSTAL TECHNIQUE:-
>useful for sample that are difficult to obtain in single crystal form.

32.  Each plane will produce a spot on photographic plate
 One can take photograph in 2 ways:-
 (i) Complete rotation method:-occurs a series of complete revolution
(ii) Oscillation method:-crystal is oscillated through an angle of 150 to 200 .

33. Adv.:- >able to measure several reflection in 1 exp.
>possibility # to separate reflections(that have same diffraction angle)
# to control the direction and range of rotation
Lim.:->Preparation/mounting of sample is difficult.
STRUCTURAL ELUCIDATION:-

34.  This technique has been developed for solving crystal str. From powder diffraction data.
 Involves an interpretation of peak positions and intensities.

35. #The analytical applications of X-ray diffraction are numerous.
#Perhaps its most important use has been to measure the size of
crystal planes.
# The patterns obtained are characteristic of the particulars compounds
from which the crystal was formed.
#For examples, as shown in figure1 NaCl crystals and KCl crystal give
different diffraction pattern.A mixture containing 1%KCl in NaCl would
show a diffraction patter of NaCl with a weak pattern of KCl.On the
other hand,a mixture containing 1%NaCl in KCl would show the
diffraction pattern of KCl with a peak pattern of NaCl.
 If, on the other hand,the crystal is a mixed crystal of sodium potassium
chloride,in which the sodium and potassium ions are in the same crystal
lattice,there would be changes in the crystal’s lattice size,as shown in
figure 2. When there is a large excess of sodium over potassium,the
pattern would be similar to that of sodium chloride.However,as the
potassium content increases,the lattice dimensions change accordingly
until they equal that of the potassium chloride

36. when there is a very large
excess of potassium chloride
present.This method can be
used to distinguish between
a mixture of crystals,which
would give both diffraction
pattern,and a mixed
crystal,which would give a
separate diffraction pattern.
Comparing diffraction patterns
from crystals of unknown
composition with patterns from
crystals of known compounds
permits the identification of
unknown crystalline
compounds
Figure 1: Hypothetical x-ray pattern of two
salts:(a)x-ray pattern of salt A,(b)x-ray pattern
of salt B,and (c)x-ray pattern of a mixture of
salts A and B.
Figure 2: X-ray pattern of a powdered mixed
crystal of A and B.Note that the peaks fall
between those in Fig.1(c),showing that lattice
size does not coincide with that of Fig.1(a) or
(b),but is between them.

38. disadvantages of this method is that spots due to strained particles are
difficult to count.
Broadening Of Diffraction Lines-This method is used for particles in the
range 30-1000Å.This method is based upon the simple fact that there is
broadening of the powder diffraction lines.for a powder composed of
perfect crystalline particles in this size range,we know.

39. Lhkl=Kλ/β0cosθ
Where Lhkl=the mean crystalline dimension (size) perpendicular to the plane (hkl),
β0= the breadth at half maximum of a pure diffraction profile in radians and
K=a constant,generally taken as unity.