X-ray crystallography uses x-ray diffraction patterns to determine the atomic structure of crystals. X-rays are produced using an x-ray tube and passed through a monochromator to produce a single wavelength. The x-rays are then directed at a crystal sample, which causes the beams to diffract into specific directions based on the crystal structure. Detectors measure the intensities and angles of the diffracted beams, which are used to reconstruct the three-dimensional electron density and atomic positions in the crystal. X-ray crystallography has applications in determining crystal structures, polymer characterization, and analyzing materials.

1. X-RAY CRYSTALLOGRAPHY
PRESENTED BY:-
MEGHA VARSHNEY
M.PHARM (PHARMACOLOGY)

2. X-RAY/RÖNTGEN RADIATION
German physicist Wilhelm Röntgen is usually credited as the discoverer of x-
rays in 1895.
X-rays are form of electromagnetic waves.
Wavelength- 0.01 to 10 nanometers.
Frequency- 3×1016 Hz to 3×1019 Hz.
Energy- 100eV to 100keV
They have shorter wavelength than UV but longer than those of Gamma radiation.

4. THEORY OF X-RAY

5. CRYSTALLOGRAPHY
Crystallography is a natural science with the scope of investigating matter in
the crystalline state.
“Crystallography“, greek words crystallon "cold drop, frozen drop”
and graphein "to write".
Before the development of x-ray crystallography, the study of crystals was
based on their geometry. This involves measuring the angles of crystal faces,
and establishing the symmetry of the crystal in question.

6. CRYSTALS
A crystal is a solid material whose constituent atoms, molecules or ions are
arranged in an orderly repeating pattern extending in all three spatial dimensions.
METTALIC CRYSTALS
•Copper, Silver, Aluminum, Tungsten,
Magnesium etc.
NON-METALLIC CRYSTALS
•Ice, Carbon, Diamond, Sodium
Chloride, Pottasium Chloride etc.

7. INTRODUCTION TO X-RAY CRYSTALLOGRAPHY
X-ray crystallography is a technique used for determining the atomic and
molecular structure of a crystal, in which the crystalline atoms cause a beam of
incident x-rays to diffract into many specific directions. By measuring the angles
and intensities of these diffracted beams, a crystallographer can produce a three-
dimensional picture of the density of electrons within the crystal. From
this electron density, the mean positions of the atoms in the crystal can be
determined, as well as their chemical bonds, their disorder, and various other
information.

8. INSTRUMENTATION
1. PRODUCTION OF X-RAY
2.COLLIMATOR
3. MONOCHROMATOR
a) FILTER
b) CRYSTAL MONOCHROMATOR
4. CRYSTAL
5. DETECTORS

9. PRODUCTION OF X-RAYS
X-rays are generated via interactions of the accelerated electrons with electrons of
tungsten nuclei within the tube anode.
As the electrons bombard the target they interact which result in the conversion of energy
into heat (99%) and x-ray photons (1%).
The x-ray photons are released in a beam with a range of energies (x-ray spectrum) out
of the window of the tube and form the basis for x-ray image formation.

10. EQUIPMENT

11. COLLIMATOR
In order to get a narrow beam of X-
rays, the X-rays generated by the
target material are allowed to pass
through a collimator which consists of
two sets of closely packed metal
plates separated by a small gap.

12. MONOCHROMATOR-
In order to monochromatize the x-rays two methods are available-
a) FILTER-
The X-ray beam may be partly monochromatized by the insertion of a suitable filter. The
table given below gives some example of suitable filter and target element combination.
TARGET ELEMENT FILTER THICKNESS
Cobalt Iron 0.012mm
Copper Nickel 0.015mm
Iron Manganese 0.011mm
Molybdenum Zirconium 0.081mm
Nickel Cobalt 0.013mm

13. b) CRYSTAL MONOCHROMATORS-
It is made up of suitable crystalline material positioned in the X-ray
beam so that angle of the reflecting planes satisfied the Bragg’s
equation for the required wavelength. The beam is split up by the
crystal into the component wavelengths in the same way as a prism
splits white light into a rainbow. The crystal used is called as analyzing
crystal.
The crystals used are made up of sodium chloride, lithium flouide,
quartz etc.

14. CURVED CRYSTAL CHROMATOR FLAT CRYSTAL CHROMATOR

15. DETECTORS
The X-ray intensities can be measured and recorded on a plane or
cylindrical photographic film. The film after exposing to X-rays is
developed. The blackening of the developed film is expressed in terms
of density units D given by-
D= log I0/I
where I0 refers to the incident intensity of X-ray
I refers to the transmitted intensity of X-ray
The value of D is measured by densitometer.

16. DIFFERENT X-RAY METHODS
1. X-RAY ABSORPTION METHOD :-
X-ray absorption spectroscopy (XAS) is a widely used technique for determining
the local geometric and/or electronic structure of matter. The experiment is usually
performed at synchrotron radiation sources, which provide intense and tunable x-
ray beams. Samples can be in the gas-phase, solution, or condensed matter (i.e.
Solids).

17. 2. X-RAY DIFFRACTION METHOD :-
X-ray powder diffraction (XRD) is a rapid analytical technique primarily used
for phase identification of a crystalline material and can provide information on
unit cell dimensions. The analyzed material is finely ground, homogenized, and
average bulk composition is determined.

18. 3. X-RAY FLUORESCENCE METHOD
XRF (x-ray fluorescence) is a non-destructive analytical technique used to
determine the elemental composition of materials. XRF analyzers determine the
chemistry of a sample by measuring the fluorescent (or secondary) x-ray emitted
from a sample when it is excited by a primary x-ray source.
It is a method for measuring the thickness of coatings and for analyzing materials.
It can be used for the qualitative and quantitative determination of the elemental
composition of a material sample as well as for measuring coatings and coating
systems.

19. BRAGG’S LAW
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 path length difference is equal to an integer number of wavelengths.

21. ROTATING CRYSTAL TECHNIQUE
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 and 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,
and at that point a diffracted beam will be formed.
The reflected beams are located on the surface of imaginary cones. When the film
is laid out flat, the diffraction spots lie on horizontal lines.

23. X-RAY POWDER TECHNIQUE
Powder diffraction is a scientific technique using x-ray, for structural
characterization of materials. A diffractometer produces waves at a
known frequency, which is determined by their source. When these
waves reach the sample, the atoms of the sample act just like
a diffraction grating, producing bright spots at particular angles. By
measuring the angle where these bright spots occur, the spacing of the
diffraction grating can be determined.

25. LAUE PHOTOGRAPHIC METHOD
a) TRANSMISSION METHOD-
In the transmission laue method, the film is placed behind the crystal.
A beam of x-ray is passed through the crystal, after passing through the
crystal, x-ray are diffracted and recorded on a photographic plate.

27. b) BACK REFLECTION METHOD-
In the back reflection method, the film is placed between the x-ray
source and the crystal. The beam which are diffracted in a backward
direction are recorded.

29. APPLICATIONS OF X-RAY
DIFFRACTION
1. Structure of Crystals-
Comparing diffraction pattern from crystals of
unknown composition with patterns from crystals
of known component permits the identification of
unknown crystalline compound.

30. 2. Polymer Characterisation-
It is used to determine the degree of crystallnity of
the polymer. The non crystalline portion simply
scatter the beam to give a continuous background,
while crystalline portion causes diffraction lines
that are not continuous.

31. 3. State of anneal in metal
If the metal is subjected to drilling, hammering, or
bending, it becomes “worked” or “fatigued”, i.e.
its crystals become broken that leads to metal
breaking, this could be checked by XRD.

32. 4. Particle size determination-
Spot counting method-
v= V.δθ.cosθ/2n
Where v= volume or size of individual crystallite,
V= total volume of specimen irradiated,
n= no. of spots in a diffraction ring at a bragg angle of θ
δθ= divergence of x-ray beam

33. 5. Determination of cis and trans isomers.
6. Determination of linkage isomerism.
7. Soil classification based on crystallinity.
8. To assess the weathering and degradation of natural and synthetic minerals.
9. The products of corrosion can be identified by XRD, also by research, the factors
that affect the corrosion rate can be determined.
10. Tooth decay and dentine have been examined by XRD.
11. Identification of crystalline compound in the body.
12. It reveals some of the effects of diseases on bone structure and tissue structure.

34. APPLICATION OF X-RAY ABSORPTION
XAS is a technique used in different scientific fields including molecular and
condensed matter physics, materials science and engineering, chemistry, earth
science, and biology. In particular, its unique sensitivity to the local structure, as
compared to x-ray diffraction, have been exploited for studying:
1. Amorphous solids and liquid systems
2. Doping and ion implantation materials for electronics
3. Local distortions of crystal lattices
4. Organometallic compounds
5. Metalloproteins
6. Metal clusters
7. Ions in solutions
8. Speciation of elements