X ray, invisible, highly penetrating electromagnetic radiation of much shorter wavelength (higher frequency) than visible light. The wavelength range for X rays is from about 10-8 m to about 10-11 m, the corresponding frequency range is from about 3 × 1016 Hz to about 3 × 1019 Hz.
X-Ray Crystallography is a technique used to determine 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.
Types of crystals & Application of x raykajal pradhan
some basic information:-
A crystal lattice is a 3-D arrangement of unit cells.
Unit cell is the smallest unit of a crystal, By stacking identical unit cells, the entire lattice can be constructed
A crystal’s unit cell dimensions are defined by six numbers, the lengths of the 3 axes, a, b, and c, and the three interaxial angles, α, β and γ.
If a unit cell has the same type of atom at the corners of the unit cell but not also in the middle of the faces nor in the centre of the cell, it is called primitive and given by symbol P
7 types of crystal system details
14 bravis lattice
APPLICATION X-RAY CRYSTALLOGRAPHY
1. Structure of crystals
2. Polymer characterisation
3. State of anneal in metals
4. Particle size determination
a) Spot counting method
b) Broadening of diffraction lines
c) Low-angle scattering
5.Applications of diffraction methods to complexes
a) Determination of cis- trans isomerism
b) Determination of linkage isomerism
6.Miscellaneous applications
X-Ray Crystallography is a technique used to determine 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.
Types of crystals & Application of x raykajal pradhan
some basic information:-
A crystal lattice is a 3-D arrangement of unit cells.
Unit cell is the smallest unit of a crystal, By stacking identical unit cells, the entire lattice can be constructed
A crystal’s unit cell dimensions are defined by six numbers, the lengths of the 3 axes, a, b, and c, and the three interaxial angles, α, β and γ.
If a unit cell has the same type of atom at the corners of the unit cell but not also in the middle of the faces nor in the centre of the cell, it is called primitive and given by symbol P
7 types of crystal system details
14 bravis lattice
APPLICATION X-RAY CRYSTALLOGRAPHY
1. Structure of crystals
2. Polymer characterisation
3. State of anneal in metals
4. Particle size determination
a) Spot counting method
b) Broadening of diffraction lines
c) Low-angle scattering
5.Applications of diffraction methods to complexes
a) Determination of cis- trans isomerism
b) Determination of linkage isomerism
6.Miscellaneous applications
Nuclear magnetic resonance (NMR) spectroscopyVK VIKRAM VARMA
SPECTROSCOPY
NMR SPECTROSCOPY
HISTORY
THEORY
PRINCIPLE
INSTRUMENTATION
SOLVENTS USED IN NMR(PROTON NMR)
CHEMICAL SHIFT
FACTORS AFFECTING CHEMICAL SHIFT
RELAXATION PROCESS
SPIN-SPIN COUPLING
푛+1 RULE
NMR SIGNALS IN VARIOUS COMPOUNDS
COUPLING CONSTANT
NUCLEAR MAGNETIC DOUBLE RESONANCE/ SPIN DECOUPLING
FT-NMR
ADVANTAGES & DISADVANTAGES
APPLICATIONS
REFERENCE
It would be use full to All Needy People. It involve information about NMR Spectroscopy ( a spectroscopic techniques), factors influencing , proton NMR and their applications of NMR as well as Nuclear magnetic imaging.
In this slide contains Principle, Methods, Interpretation and applications of XRD.
Presented by: Udit Narayan Singh (Department of pharmaceutics)
RIPER, anantpur.
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.
Nuclear magnetic resonance (NMR) spectroscopyVK VIKRAM VARMA
SPECTROSCOPY
NMR SPECTROSCOPY
HISTORY
THEORY
PRINCIPLE
INSTRUMENTATION
SOLVENTS USED IN NMR(PROTON NMR)
CHEMICAL SHIFT
FACTORS AFFECTING CHEMICAL SHIFT
RELAXATION PROCESS
SPIN-SPIN COUPLING
푛+1 RULE
NMR SIGNALS IN VARIOUS COMPOUNDS
COUPLING CONSTANT
NUCLEAR MAGNETIC DOUBLE RESONANCE/ SPIN DECOUPLING
FT-NMR
ADVANTAGES & DISADVANTAGES
APPLICATIONS
REFERENCE
It would be use full to All Needy People. It involve information about NMR Spectroscopy ( a spectroscopic techniques), factors influencing , proton NMR and their applications of NMR as well as Nuclear magnetic imaging.
In this slide contains Principle, Methods, Interpretation and applications of XRD.
Presented by: Udit Narayan Singh (Department of pharmaceutics)
RIPER, anantpur.
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.
Production of X rays, Different X ray diffraction methods, Bragg‘s law, Rotating crystal technique, X ray powder technique, Types of crystals and applications of X-ray Diffraction
Crystal Structures and X-Ray Diffraction - Sultan LeMarcslemarc
Report on the investigation of the characteristics of X-rays by measuring the count rate of X-rays reflected off alkali halide crystals at varying angles of incidence and using the principles of Bragg’s law. The experiment probes into crystal structures using X-ray diffractometry and deduces the lattice constants and ionic radii using the Miller index notation. The experiment successfully computes the characteristic wavelengths of Copper and clearly demonstrates the effect of filters on spectrum intensities. The interpretation of Miller indices and diffraction patterns are effectively used to analyse crystalline structures and compare lattice arrangements. By Sultan LeMarc
WHO defines Quality of Life as an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns.
Principles of essentiality
Principles of voluntariness, informed consent and community agreement
Principles of non-exploitation
Principles of privacy and confidentiality
Principles of precaution and risk minimisation
Principles of professional competence
Principles of accountability and transparency
Formulary is an official or authorised publication of an approved list of medicines for use in a hospital, a group of hospitals a society a state or a region a country or a number of countries.
Hospital Formulary is a continually revised compilation of pharmaceuticals dosage agents and their forms that reflects the current clinical view of the medical staff.
PHARMACY AND THERAPEUTICS COMMITTEES AND THE HOSPITAL FORMULARYHealth Forager
Almost every patient who is admitted to a hospital receives drug therapy. Drug therapy accounts for a substantial percentage of cost to an institution. While drugs are life saving, they also have the potential to cause morbidity and mortality. The Pharmacy and Therapeutics (P&T) Committee stands as the decision-making body concerning drug use for most institutions. The concept of a P&T Committee has been around for decades; however, the committee has become substantially more important over the past 20 years. This committee is paramount to the drug decision process in hospitals. Formularies stem from P&T Committees and help provide useful, cost-effective, and safe therapeutic choices to clinicians. This chapter explores in detail the P&T Committee and the use of formularies in an institutional setting.
Drug distribution is one of the basic service provided by the hospital pharmacy.
Drug distribution system falls in to 3 categories -
1)Ward – controlled system
2)Pharmacy controlled imprest based system
3)Pharmacy controlled patient issue system
Drug induced skin disorders is defined as any skin disorders caused by a drug or medication. It is estimated that 2—3 percent of hospitalised patients are affected by a drug eruption, and that serious drug eruptions occur in around 1 in 1000 patients.
CONTENTS :
INTRODUCTION
TRANSPARENCY
PROMOTING RESEARCH INTEGRITY
EDITORIAL STANDARDS AND PROCESSES
RESPONSIBLE PUBLICATION PRACTICES
OWNERSHIP OF IDEAS AND EXPRESSION
- Video recording of this lecture in English language: https://youtu.be/lK81BzxMqdo
- Video recording of this lecture in Arabic language: https://youtu.be/Ve4P0COk9OI
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Ozempic: Preoperative Management of Patients on GLP-1 Receptor Agonists Saeid Safari
Preoperative Management of Patients on GLP-1 Receptor Agonists like Ozempic and Semiglutide
ASA GUIDELINE
NYSORA Guideline
2 Case Reports of Gastric Ultrasound
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Anti ulcer drugs and their Advance pharmacology ||
Anti-ulcer drugs are medications used to prevent and treat ulcers in the stomach and upper part of the small intestine (duodenal ulcers). These ulcers are often caused by an imbalance between stomach acid and the mucosal lining, which protects the stomach lining.
||Scope: Overview of various classes of anti-ulcer drugs, their mechanisms of action, indications, side effects, and clinical considerations.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
1. I. X-Ray
II. Diffraction
III. Diffraction of Waves by Crystals
IV. X-Ray Diffraction
V. Bragg Equation
VI. X-Ray Methods
1
2. X-RAY
X-rays were discovered in
1895 by the German physicist
Wilhelm Conrad Röntgen and
were so named because their
nature was unknown at the
time.
He was awarded the Nobel
prize for physics in 1901.
2
Wilhelm Conrad Röntgen
(1845-1923)
3. X-RAY PROPERTIES
3
X ray, invisible, highly penetrating electromagnetic radiation of
much shorter wavelength (higher frequency) than visible light.
The wavelength range for X rays is from about 10-8
m to about 10-11
m, the corresponding frequency range is from about 3 × 1016
Hz to
about 3 × 1019
Hz.
4. PRODUCTION OF X-RAYS
Visible light photons and X-ray photons are both produced
by the movement of electrons in atoms. Electrons occupy
different energy levels, or orbitals, around an atom's
nucleus.
When an electron drops to a lower orbital, it needs to
release some energy; it releases the extra energy in the form
of a photon. The energy level of the photon depends on
how far the electron dropped between orbitals.
4
5. 5
Evacuated glass bulb
Anode
Cathode
X rays can be produced in a highly evacuated glass bulb, called
an X-ray tube, that contains essentially two electrodes—an
anode made of platinum, tungsten, or another heavy metal of
high melting point, and a cathode. When a high voltage is
applied between the electrodes, streams of electrons (cathode
rays) are accelerated from the cathode to the anode and
produce X rays as they strike the anode.
X-RAY TUBE
6. Monochromatic and Broad
Spectrum of X-rays
X-rays can be created by bombarding a metal target with high
energy (> ) electrons.
Some of these electrons excite electrons from core states in the
metal, which then recombine, producing highly
monochromatic X-rays. These are referred to as characteristic
X-ray lines.
Other electrons, which are decelerated by the periodic
potential of the metal, produce a broad spectrum of X-ray
frequencies.
Depending on the diffraction experiment, either or both of
these X-ray spectra can be used. 4
10
6
4
10
7. Absorption of X-rays
A larger atom is more likely to absorb an X-ray photon in
this way, because larger atoms have greater energy
differences between orbitals -- the energy level more closely
matches the energy of the photon. Smaller atoms, where the
electron orbitals are separated by relatively low jumps in
energy, are less likely to absorb X-ray photons.
The soft tissue in your body is composed of smaller atoms,
and so does not absorb X-ray photons particularly well. The
calcium atoms that make up your bones are much larger, so
they are better at absorbing X-ray photons.
7
10. 10
Target Metal λ Of Kα radiation (Å)
Mo 0.71
Cu 1.54
Co 1.79
Fe 1.94
Cr 2.29
11. Intensity
Wavelength (λ)
Mo Target impacted by electrons accelerated by a 35 kV potential
0.2 0.6 1.0 1.4
White
radiation
Characteristic radiation →
due to energy transitions
in the atom
Kβ
Kα
12. X ray DIFFRACTION
Diffraction is a wave phenomenon in which the apparent
bending and spreading of waves when they meet an
obstruction.
In crystals the regularly spaced atoms acts as natural gratings.
Since the atoms are large in their size, the inter atomic
distance of atoms are in order of the wavelength of x-ray.
Hence the atoms of crystals are able to diffract x-ray
Mode of diffraction is different for different crystals due to
vary in their inter atomic and inter planar distances
and hence the diffracted rays produce unique pattern on
radiographic films which are finger prints for every crystals
Hence x-ray diffraction technique is a powerful tool for the
qualitative study of crystals
12
17. Bragg Equation
Bragg law identifies the angles of the incident
radiation relative to the lattice planes for which
diffraction peaks occurs.
Bragg derived the condition for constructive
interference of the X-rays scattered from a set of
parallel lattice planes.
17
18. BRAGG EQUATION
W.L. Bragg considered crystals to be made up of parallel planes
of atoms. Incident waves are reflected specularly from parallel
planes of atoms in the crystal, with each plane is reflecting only
a very small fraction of the radiation, like a lightly silvered
mirror.
In mirrorlike reflection the angle of incidence is equal to the
angle of reflection.
18
өө
19. Bragg Equation
When the X-rays strike a layer of a crystal, some of them will be
reflected. We are interested in X-rays that are in-phase with
one another. X-rays that add together constructively in x-ray
diffraction analysis in-phase before they are reflected and after
they reflected.
θ
19
Incident angle
Reflected angle
Wavelength of X-ray
Total Diffracted
Angle
θ =
θ =
λ =
θ 2θ
θ2=
20. 20
Bragg Equation
These two x-ray beams travel slightly different distances. The
difference in the distances traveled is related to the distance
between the adjacent layers.
Connecting the two beams with perpendicular lines shows the
difference between the top and the bottom beams.
The line CE is equivalent
to the distance between
the two layers (d)
sinDE d θ=
21. Bragg Law
The length DE is the same as EF, so the total distance
traveled by the bottom wave is expressed by:
Constructive interference of the radiation from successive
planes occurs when the path difference is an integral number
of wavelenghts. This is the Bragg Law.
sinEF d θ=
sinDE d θ=
21
2 sinDE EF d θ+ =
2 sinn dλ θ=
22. Bragg Equation
where, d is the spacing of the planes and n is the order of diffraction.
Bragg reflection can only occur for wavelength
This is why we cannot use visible light. No diffraction occurs when
the above condition is not satisfied.
The diffracted beams (reflections) from any set of lattice planes can
only occur at particular angles pradicted by the Bragg law.
λθ nd =sin2
22
dn 2≤λ
23. Types of X-ray methods
There are many types of X-ray camera to sort out
reflections from different crystal planes. We will study
only three types of X-ray photograph that are widely
used for the simple structures.
1. Laue photograph
2.Rotating crystal method
3. Powder photograph
23
25. LAUE METHOD
The Laue method is mainly used to determine the
orientation of large single crystals while radiation is
reflected from, or transmitted through a fixed crystal.
25
The diffracted beams form arrays of
spots, that lie on curves on the film.
The Bragg angle is fixed for every set
of planes in the crystal. Each set of
planes picks out and diffracts the
particular wavelength from the white
radiation that satisfies the Bragg law for
the values of d and θ involved.
26. Back-reflection Laue Method
In the back-reflection method, the film is placed between the
x-ray source and the crystal. The beams which are diffracted in
a backward direction are recorded.
26
One side of the cone of Laue
reflections is defined by the
transmitted beam. The film
intersects the cone, with the
diffraction spots generally lying
on an hyperbola.
X-Ray Film
Single
Crystal
27. Transmission Laue Method
In the transmission Laue method, the film is placed behind
the crystal to record beams which are transmitted through
the crystal.
27
One side of the cone of Laue
reflections is defined by the
transmitted beam. The film
intersects the cone, with the
diffraction spots generally
lying on an ellipse.
X-Ray
FilmSingle
Crystal
28. Laue Pattern
28
The symmetry of the spot
pattern reflects the symmetry of
the crystal when viewed along
the direction of the incident
beam. Laue method is often
used to determine the
orientation of single crystals by
means of illuminating the crystal
with a continuos spectrum of X-
rays;
Single crystal
Continous spectrum of x-rays
Symmetry of the crystal;
orientation
29. 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 and the
crystal is rotated about the
chosen axis.
29
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.
30. Rotating Crystal Method
The reflected beams are located on the surface of imaginary
cones. By recording the diffraction patterns (both angles and
intensities) for various crystal orientations, one can determine
the shape and size of unit cell as well as arrangement of atoms
inside the cell.
30
Film
31. THE POWDER METHOD
If a powdered specimen is used, instead of a
single crystal, then there is no need to rotate the
specimen, because there will always be some
crystals at an orientation for which diffraction is
permitted. Here a monochromatic X-ray beam is
incident on a powdered or polycrystalline sample.
This method is useful for samples that are
difficult to obtain in single crystal form.
31
32. THE POWDER METHOD
The powder method is used to determine the value of
the lattice parameters accurately. Lattice parameters are
the magnitudes of the unit vectors a, b and c which
define the unit cell for the crystal.
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.
32
33. The Powder
Method
If a monochromatic x-ray beam is
directed at a single crystal, then only
one or two diffracted beams may
result.
33
If the sample consists of some tens of
randomly orientated single crystals, the
diffracted beams are seen to lie on the
surface of several cones. The cones may
emerge in all directions, forwards and
backwards.
A sample of some hundreds of
crystals (i.e. a powdered
sample) show that 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 film.
34. Debye Scherrer Camera
A very small amount of powdered material is sealed into
a fine capillary tube made from glass that does not diffract
x-rays.
34
The specimen is placed
in the Debye Scherrer
camera and is accurately
aligned to be in the centre
of the camera. X-rays enter
the camera through a
collimator.
35. Debye Scherrer Camera
The powder diffracts the
x-rays in accordance with
Braggs law to produce
cones of diffracted beams.
These cones intersect a
strip of photographic film
located in the cylindrical
camera to produce a
characteristic set of arcs on
the film.
35
36. Powder diffraction film
When the film is removed from the camera,
flattened and processed, it shows the diffraction
lines and the holes for the incident and
transmitted beams.
36
37. Application of XRD
1. Differentiation between crystalline and amorphous
materials;
2. Determination of the structure of crystalline materials;
3. Determination of electron distribution within the atoms, and
throughout the unit cell;
4. Determination of the orientation of single crystals;
5. Determination of the texture of polygrained materials;
37
XRD is a nondestructive technique. Some of the uses of x-ray
diffraction are;
38. Advantages and disadvantages
of X-rays
Advantages;
X-ray is the cheapest, the most convenient and widely
used method.
X-rays are not absorbed very much by air, so the specimen
need not be in an evacuated chamber.
Disadvantage;
They do not interact very strongly with lighter elements.
38