X-RAY DIFFRACTION

BY

Fatma Defne KocaayanBuket Sinem Gökhan Cesur

HISTORY OF X-RAY DIFFRACTION

1895: Roentgen discovered x-rays  1912: von Laue, Friedrich, and Knipping

passed x-rays through crystal of ZnS and concluded that:

  a) Crystals are composed of periodic arrays of atomsb) Crystals cause distinct x-ray diffraction

patterns due to atoms

1914: Bragg and Lawrence showed that diffraction pattern can be used to determine relative positions of atoms within a single crystal (i.e., molecular structure)

1953 : Rosalind Franklin: collected X-ray diffraction data on Na salt of DNA .Guides Watson and Crick to determine that DNA is a double helix.

HISTORY OF X-RAY DIFFRACTION

NOW: Determined atomic structures and in medical applications

HISTORY OF X-RAY DIFFRACTION

WHAT İS X-RAY DİFFRACTİON ?

WHAT İS X-RAY DİFFRACTİON ?

Based on constructive interference of monochoromatic –rays and crystalline sample

BRAGG’S LAW

Crystals composed of parallel atomic planes 

incoming waves undergo reflection separetly from each plane

reflected light creates  interference patterns

BRAGG’S LAW

İncoming angle equals to reflection angle

BRAGG’S LAW Path lenght must equal integer multiples of

wavelength (BRAGG’S differraction rule) This rule are shown with the Bragg’s

equation

nd sin2

BRAGG’S LAW

If the bragg’s equation is Not satisfied NO REFLECTION can occur,

If the bragg’s equation is satisfied REFLECTION may occur,

INSTRUMANTATION

The instrumantation consist of four parts and they are;

Production of x-rays Collimator Monochromators Detector

PRODUCTION OF X-RAYS X-rays are generated when

high velocity electrons impinge on a metal target which are having high melting point,good thermal conductivity and large atomic number.Such as silver, iron,copper,tungsten.

Approximately 1% of the total energy of the beam is converted into x-rays.

The reminder being dissipated as heat.

COLLIMATOR

A series of closely spaced parallel metal plates.

The collimator absorbs all the x-rays except the narrow beam that passes between gap.

MONOCHROMATORS

Absorb the undesireable radiation and allows required wavelength to pass.There is two types of monochromator;

Filter : Using only short wavelength.Zirconium

Crystal : Using variety wavelength.Sodium Chloride, Lithium Floride

DETECTOR

The x-ray intensities can be measured and recorded either by photographic or counter methods.

Both these thypes of methods depends upon ability of x-rays to ionize matter and differ only in the subsequent fate of electrons produces by ionizing process.

TYPES OF DETECTOR

Photographic Method In order to record position

and intensity of x-ray beam a plane cylindrical film is used.

Counter Methods Geiger-Muller tube

counter(the most common) Propertional counter Scintillation counter Solid-state semi conducter

detector Semiconductor detector

HOW DOES IT WORK ?

X-Rays are generated by cathode ray tube,

Filtered to produce monochromatic radiation,

Collimated to concentrate and directed towards the sample,

The interaction of rays with the sample produces constructive interference.

HOW DOES IT WORK ? Diffraction patterns are recorded on a

photographic film.

APPLICATIONS OF X-RAY DİFFRACTION

Find structure to determine function of proteins

Example : To determine the DNA structure

Differentiation between crystalline and amorphous materials;

Determination of the structure of crystalline materials (crystal axes, size and shape of the unit cell, positions of the atoms in the unit cell)

APPLICATIONS OF X-RAY DİFFRACTION

Study crystal deformation and stress properties

APPLICATIONS OF X-RAY DİFFRACTION

Measurement of limits of solid solubility, and determination of phase diagrams;

Measurement of strain and small grain size;

APPLICATIONS OF X-RAY DIFFRACTION

Study of rapid biological and chemical processes

In health sector

Example : Qualitative Analysis Of Mineral

Qualitative Analysis Of Kidney Stone

APPLICATIONS OF X-RAY DIFFRACTION