X-ray crystallography uses X-rays to determine the atomic and molecular structure of crystals. Wilhelm Röntgen discovered X-rays in 1895. X-rays are produced when high velocity electrons collide with a metal target. X-ray crystallography works by firing a beam of X-rays at crystalline solids and observing the diffraction pattern of scattered X-rays. Bragg's law describes the conditions under which constructive interference of X-rays occurs and can be used to determine crystal structures. Common methods include rotating crystal, powder diffraction, and using detectors like photographic film, Geiger-Müller counters, or scintillation counters. X-ray crystallography has applications in determining protein structures and identifying

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X- ray crystallography
ISF COLLEGE OF PHARMACY
Department of pharmacology
Prepared by:-
Shriyansh
Srivastav
Submitted to:-
Dr. Pooja Chawla

2. Contents
2
 Introduction
 History of X rays
 Production of X rays
 X ray diffraction
 Bragg’s law
 Crystal structures
 X ray diffraction methods
 Instrumentation
 Applications

3. INTRODUCTION
3
 X-ray crystallography (XRC) is the experimental science
determining the atomic and molecular structure of the crystal, in
which the crystalline structure causes a beam of incident x-
rays to diffract into many specific direction
 X-ray crystallography is a powerful technique for visualizing the
structure of protein.

4. History of X- rays
4
 X ray were discovered in 1895 by the German physicist
‘Wilhelm conrad rontgen’and were so named because their
nature was unknown at that time.
 He was awarded the nobel prize for physics in 1901.

5. What are X- rays?
5
 X-rays are electromagnetic waves with wavelengths in the range of 0.01 to 10
nanometers,
 For analytical purpose of X ray 0.07 to 0.2 nanometers is most useful.

6. How X- rays are produced?
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 X-Ray are produced by two method -
 (a) When high velocity of electron will knock out the electron from target atom,
and due to loss of energy X-ray will produce.
 (b) High velocity of electron will strike the anode material in a discharge tube
which result production of X-rays.

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8. X- ray
diffraction
X- ray
absorption
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 It is based on scattering of x
rays by crystals
 This method is used for
identify the crystal structure of
any solid compound with high
degree of specification and
accuracy
 It is based on the principle of absorption of x
rays by the sample
 When a beam of x ray pass through the
sample and the fraction of light absorbed is
considered to be the measure of
concentration of sample
 It gives information about the absorbing
X ray florescence
It is the emission of characteristic
secondary x rays from a material that
has been excited by being
bombarded with high energy x rays ,
and by measuring the wavelength
and intensity of the generated x rays
analyst can perform qualitative and
quantitative analysis
Different phenomenon caused by x ray irradiation

9. X ray diffraction
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 X-ray diffraction, a phenomenon in which the atoms of a crystal by virtue of their uniform
spacing, cause an interference pattern of the waves present in an incident beam of X rays.
When X rays strike the crystal, the crystal diffracts the X-ray beam differently, depending on
its structure and orientation. The diffracted X-ray is collected by an area detector. The
diffraction pattern consists of reflections of different intensity which can be used to determine
the structure of the crystal.
 The resolution of an X-ray diffraction detector is determined by the Bragg equation.
When x-rays are scattered from a crystal lattice, peaks of scattered intensity are observed
which correspond to the following conditions:
 The angle of incidence = angle of scattering.
 The pathlength difference is equal to an integer number of wavelengths.
 The condition for maximum intensity contained in Bragg's law above allow us
to calculate details about the crystal structure, or if the crystal structure is known,
to determine the wavelength of the x-rays incident upon the crystal.

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12. Crystal structure
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 In crystallography, the terms crystal system, crystal family, and lattice
system each refer to one of several classes of space groups, lattices, point
groups, or crystals
 The simplest repeating unit in a crystal is called a unit cell. Each unit cell is
defined in terms of lattice points. The points in space about which the particles
are free to vibrate in a crystal. There are 7 different kinds of crystal systems, and
each kind of crystal system has 4 different kinds of centerings (Primitive, Base-
centered, Body-centered, Face-centered). However, not all of the combinations
are unique; some of the combinations are equivalent while other combinations
are not possible due to symmetry reasons.

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15. Rotating crystal method
In the Rotating crystal method, a
single crystal is mounted with an
axis normal to a monochromatic
x-ray beam. A cylindrical film is
placed around it & the crystal is
rotated about the chosen
axis. As the crystal rotates, Sets
of lattice planes will at some
point make the correct Bragg
angle for the monochromatic
incident beam, & at that point a15

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The Lattice constant of the crystal can be determined with this
method. For a given wavelength λ if the angle θ at which a
reflection occurs is known, d can be determined by using
Bragg’s Law.
The reflected beams are located on the surfaces of imaginary
cones. By recording the diffraction patterns (both angles &
intensities) for various crystal orientations, one can determine
the shape & size of unit cell as well as the arrangement of atoms
inside the cell.

17. Powder diffraction method
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If a powdered crystal is used instead of a
single crystal, then there is no need to rotate
it, because there will always be some small
crystals at an orientation for which diffraction
is permitted. Here a monochromatic X-ray
beam is incident on a powdered or
polycrystalline sample. Useful for samples
that are difficult to obtain in single crystal
form. The powder method is used to
determine the lattice parameters accurately.
Lattice parameters are the magnitudes of the
primitive vectors a, b and c which define the

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 For every set of crystal planes, by chance, one or more crystals will be in
the correct orientation to give the correct Bragg angle to satisfy Bragg's
equation.
 Every crystal plane is thus capable of diffraction. Each diffraction line is
made up of a large number of small spots, each from a separate crystal.
 Each spot is so small as to give the appearance of a continuous line
 If a monochromatic X-ray beam is directed at a single crystal, then only one
or two diffracted beams may result.
 For a sample of several randomly orientated single crystals, the diffracted
beams will lie on the surface of several cones.
 The cones may emerge in all directions, forwards and backwards For a
sample of hundreds of crystals (powdered sample), the diffracted beams
form continuous cones.
 A circle of film is used to record the diffraction pattern as shown. Each cone
intersects the film giving diffraction lines. The lines are seen as arcs on the

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 Production of x rays
 Collimator
 Monochromator
1)Filter
2) Crystal monochromator
 Detectors
1)Photographic methods
2)Counter methods
Instrumentation

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 Monochromator: The main goal of monochromator is to separate and
transmit a narrow portion of optical signals chosen from a wider range of
wavelength available at the input
1. FILTER: A filter is a window of material that absorbs undesirable radiation but allows the radiation of
required wavelength to pass. e.g.. Zirconium filter which is used for molybdenum radiation.
2. Crystal monochromator:- It is made up of a suitable crystalline material positioned in the x ray beam so
that angle of reflecting planes satisfied the Bragg's equation for required wavelength. e.g. flat crystal
monochromator
 Collimators:- collimator is a device that narrows a beam of particles or
waves. Narrow means to cause the directions of motion to become more
aligned in a specific direction. It is achieved by using a series of closely
spaced, parellel metal plates r by a bundle of tubes, 0.5 or less in
diameter

21. Detectors
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 1) Photographic methods:- This is used to determine crystal
structure
 2)Counter Methods :- This is used to determine the intensity of
x rays
It includes:-
-Geiger muller counter
-Scintillation detector

22. Photographic method
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23. Geiger muller counter
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24. Scintillation detector
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Applications of XRD
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 Determination of the structure of the crystals
 Polymers characterisation
 Differentiation between amorphous and crystalline
structure
 Determination of the orientation of the crystalline
structure
 Analysis of milk stone
 Identification of the impurity
 Identification of the fine grained minerals

26. Reference
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 Chatwal R G, Anand K S, “Instrumental method of
chemical analysis”, Himalaya publishing house, Page
no:2.303-2.339
 Kamboj C P, “Pharmaceutical analysis- 2 instrumental
method” , Vallabh publication, page no:461-483
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