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

W HAT IS X- RAY D IFFRACTION ?

 Based on constructive interference of monochoromatic –rays and crystalline sample

B RAGG ’ S L AW Crystals composed of parallel atomic planes incoming waves undergo reflection separetly from each plane reflected light creates interference patterns

B RAGG ’ S L AW İncoming angle equals to reflection angle

B RAGG ’ S L AW Path lenght must equal integer multiples of wavelength (BRAGG’S differraction rule) This rule are shown with the Bragg’s equation

B RAGG ’ S L AW  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.

T YPES OF D ETECTOR 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

H OW D OES I T W ORK ? 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.

H OW D OES I T W ORK ? 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;solubility 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