Question

Discuss the importance and key role of Bragg’s law in X-ray diffraction experiments.

Describe the developments in experimental approaches, advances in instrumentation and techniques in X-ray diffraction experiments from the era of von
Laue to the present day.

The relative intensity of Bragg reflections in X-ray powder diffraction experiments is affected by several factors. Discuss these factors and how these issues arise with an explanation of how they are corrected (with the use of suitable diagrams where appropriate).

Compare and contrast X-ray diffraction techniques with Nuclear Magnetic Resonance (NMR) in the determination of the chemical and molecular structure of inorganic microcrystalline powders.

Answer 1

Ans: when X rays are incident on a crystal face, they penetrate in to the crystal and strike the atoms in different planes, X rays are deflected . Bragg's represented a relationship between the wavelength of the X rays and the distance between the planes.

n=2dsin

where

n is integer

d is distance between planes

is angle of deflection

is wavelength

Instrumentation and techniques in X-ray diffraction experiments:

Laue's technique: In this technique is fixed, is varies different wavelengths present in the white radiations select the appropriate reflecting planes out of the the numerous present in the crystal such that the Bragg's condition is satisfied.

Rotating crystal method: A single crystal is held in the path of monochromatic radiations and rotated about an axis that is is fixed while varies. different sets of parallel atomic planes are exposed to incident radiations for different values of and reflections take place it satisfied the bragg's law.

Power method: Modern X rays crystal analysis uses an X ray diffractometer which has a radiation counter to detect the angle and intensity of the diffraction beam.

X-ray diffraction techniques are used to identified physical and chemical properties of crystals.

Nuclear Magnetic Resonance (NMR) is used to determined reservoir permeability and reduce or eliminate water production.