X-RAY DIFFRACTION

BY

Fatma Defne Kocaayan

Buket 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 atoms

b) 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 IS X-RAY DIFFRACTION ?

WHAT IS X-RAY DIFFRACTION ?

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