X-ray diffraction is a technique used to determine the atomic and molecular structure of crystals. When an X-ray beam hits a crystal, the beam diffracts into specific directions based on the atomic planes in the crystal. Bragg's law describes the diffraction pattern and is used to explain the angles and wavelengths of the diffracted X-rays. To collect diffraction data, crystals are mounted on a goniometer and bombarded with X-rays while being rotated, producing a diffraction pattern. The pattern can then be analyzed to determine information about the crystal structure like lattice parameters and atomic arrangement.

1. X-Ray Diffraction
Praveen Kumar
Central University of Bihar
School of Earth Biological and Environmental Sciences

2. An electromagnetic wave of high energy and very short
wavelength (between ultraviolet light and gamma
rays), which is able to pass through many materials
opaque to light.
Energy : 100 eV to 100keV
Wavelength : 0.01 to 10 nanometer
X Ray
Why are x-
rays used?
λ ~ Å

3. The process by which a beam of light or other
system of waves is spread out as a result of passing
through a narrow aperture or across an edge,
typically accompanied by interference between the
wave forms produced.
Diffraction

4. X Ray Diffraction
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.
The atomic planes of a crystal cause an incident beam of X-
rays to interfere with one another as they leave the crystal. The
phenomenon is called X-ray diffraction.
A stream of X-rays directed at a crystal diffract and scatter as
they encounter atoms. The scattered rays interfere with each
other and produce spots of different intensities that can be
recorded on film.

5. Working Principle
Bragg’s Law
Bragg's law was used to explain the interference
pattern of X-rays scattered by crystals
Nλ = 2dhkl sinθ
q q
dhkldhkl

6. Experimental Setup
Source: http://pruffle.mit.edu/atomiccontrol/education/xray/xray_diff.php

7. How Does It WorkSource:http://en.wikipedia.org/wiki/File:X_ray_diffraction.png
Crystal (regular array of atoms) is
mounted on a Goniometer
Bombarded with X-Ray while
rotating
Production of diffraction pattern
of regularly spaced spots
The 2-D images taken at different
rotation are converted to 3-D
models of the electron density map
by the method of Fourier
Transform

8. Some Example Images

9. Uses
 XRD is a non-destructive technique.
 To determine structural properties such as Lattice
parameters (10-4Å), strain, grain size
 Biological macromolecular crystallography
 To determine atomic arrangement.
 To measure thickness of thin films and multi-layers.

10. Thanks