2. CONTENTS:
Introduction
Origin of x-rays
Basic aspects of crystals
Miller indices
X-ray crystallography
Methods of XRD
Applications
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3. INTRODUCTION:
It is a novel and non-destructive method of
chemical analysis and variety of X-ray techniques
are available now a days in practice.
Different techniques: X-ray Absorption
X-ray Diffraction
X-ray Fluorescence
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4. ORIGIN OF X-RAYS:
EM Radiations
Wavelength: 0.01 to 10nm.
Frequency: 30 petaHz to 30 exaHz.
Energy: 100eV to 100keV.
Sources:
1. Production by electrons
2. Production by fast positive ions
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*Ref:Chatwal,Pg.no.2.303
5. BASIC ASPECTS OF
CRYSTALS:
Unit cell:
Length of cell edges
Angles between them
Position off atoms in unit cells
Crystal lattice:
Triclinic Monoclinic Orthorhombic
Tetragonal Hexagonal Cubic
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*Ref:Wikipedia-crystalstructure
6. MILLERS INDICES:
Denoted by h, l, k values
Helps to understand the
dimensions of cube
Equation:
d= spacing between
adjacent lattice
a= lattice constant
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*Ref:Wikipedia:MillerIndices
7. X-RAY DIFFRACRTION:
Principle:
“When X-ray are passed on crystal, they get
scattered based on the arrangement of atoms in
crystal.”
“Every crystalline substance gives a pattern; the
same substances always gives same pattern; and in
mixture of substance, each produce it’s pattern
independent of other.”
Definition:
The atomic planes of crystals cause an incident beam of X-
rays to interfere with one another as they leave the crystal.
This is called as XRD.
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*Ref:Chatwal-2.303;Willards-340
22. 1. LAUE METHOD
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Single crystal is held stationary in a beam of X-ray or
neutron radiation of continuous wavelength
Crystal selects out and diffracts the discrete values of θ
for which planes exist of spacing d and incidence angle
λ
Method is convenient for the rapid determination of
crystal orientation and symmetry.
*Ref:Chatwal-2.318
23. 2. BRAGG’S X-RAY SPECTROPHOTOMETER
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X-rays
Pass from slits
Falls on C
(Vertically rotating about it’s axis)
Reflected beam pass to Ionization chamber
Ionization of gas
Current measured by Galvanometer
Intensity of reflected X-ray is measured.
The ionization current is measured for
different values of glancing angle θ. A
graph is drawn between the glancing angle
θ and ionization current.
*Ref:Chatwal-2.319
24. 2. BRAGG’S X-RAY SPECTROPHOTOMETER
(CNTD):
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For certain values of glancing
angle, the ionization current
increases abruptly.
The first peak corresponds to
first order, the second peak to
second order and so on. From
the graph, the glancing angles
for different orders of reflection
can be measured.
Knowing the angle θ and the
spacing d for the crystal,
wavelength of X–rays can be
determined
*Ref:Chatwal-2.319
25. 3. ROTATING CRYSTAL TECHNIQUE
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Crystal is rotated about fixed
axis.
Variation in angle θ
Dimensions of crystal <1mm
The beam is diffracted from a
given crystal plane whenever
in the course of rotation the
value of θ satisfies the Bragg
equation.
Beams from all planes parallel
to the vertical rotation axis will
lie in the horizontal plane.
Planes with other orientations
will reflect in layers above and
below the horizontal plane.
*Ref:Chatwal-2.324
26. 4. POWDER METHOD:
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The incident monochromatic radiation strikes a finely
powdered specimen or a fine grained polycrystalline
specimen contained in a thin walled capillary tube.
Diffracted rays go out from individual crystallites which
happened to be oriented with planes making an incident
angle θ with the beam satisfying the Bragg equation.
This method is known to be the most fast and accurate for
the determination of lattice constants.
*Ref:Chatwal-2.324
28. X-ray powder diffraction is most widely used for the
identification of unknown crystalline materials (e.g. minerals,
inorganic compounds). Determination of unknown solids is
critical to studies in geology, environmental science,
material science, engineering and biology. Other
applications include:
Characterization of crystalline materials
Identification of fine-grained minerals such as clays and
mixed layer clays that are difficult to determine optically
Determination of unit cell dimensions
Measurement of sample purity
With specialized techniques, XRD can be used to:
Determine crystal structures using Rietveld refinement
Determine of modal amounts of minerals (quantitative analysis)
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APPLICATIONS:
*Ref:Chatwal-2.326,Willards:370
29. PHARMACEUTICAL APPLICATIONS
(R&D):
Crystal characterization of Acrinol
Compaction Characteristics of bulk crystalline powders
Polymorphism of Piracetam
Evaluation of physical stability of Amoxicillin Trihydrate.
Detection of solvatomorphism
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*Ref:Chatwal-2.326,Willards:370
30. REFERENCES:
1. Instrumental Methods of Analysis by Willard, Merritt, Dean,
Settle, CBS Publishers & Distributors, 7th Edition, Page No.
340 – 397
2. Instrumental Methods of Chemical Analysis by Gurdeep R.
Chatwal & Sham K. Anand, Himalaya Publications, 5th revised
edition, Page no. 2.303 – 2.339
3. http://www.slideshare.net/gopinathkarnam/x-ray-diffraction-
25472126
4. https://en.wikipedia.org/wiki/Crystal_structure#Unit_cell
5. http://serc.carleton.edu/research_education/geochemsheets/te
chniques/XRD.html
6. http://ictwiki.iitk.ernet.in/wiki/index.php/Unit-
2:_Introduction_to_X-ray_diffraction#ROTATING-
CRYSTAL_METHOD
7. Lecture 1.pdf
8. Han J, Suryanarayanan R. A method for the rapid evaluation of
the physical stability of pharmaceutical hydrates.
Thermochimica acta. 1999 Apr 26;329(2):163-70.
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31. REFERENCES OF RESEARCH
ARTICLES:
1. Brittain HG. X-ray diffraction of pharmaceutical materials. Profiles of
Drug Substances, Excipients and Related Methodology. 2003 Dec
31;30:271-319.
2. Han J, Suryanarayanan R. A method for the rapid evaluation of the
physical stability of pharmaceutical hydrates. Thermochimica acta. 1999
Apr 26;329(2):163-70.
3.Moore MD, Steinbach AM, Buckner IS, Wildfong PL. A structural
investigation into the compaction behavior of pharmaceutical
composites using powder X-ray diffraction and total scattering analysis.
Pharmaceutical research. 2009 Nov 1;26(11):2429-37.
4. Croker DM, Hennigan MC, Maher A, Hu Y, Ryder AG, Hodnett BK. A
comparative study of the use of powder X-ray diffraction, Raman and
near infrared spectroscopy for quantification of binary polymorphic
mixtures of piracetam. Journal of pharmaceutical and biomedical
analysis. 2012 Apr 7;63:80-6.
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