In the last few lectures, we have covered

• X-ray diffraction for analyzing the phase, indexing and lattice parameter calculations. œ

• Analytical line profile fitting using various models.

In the next few lectures, we shall focus on other diffraction techniques such as neutron diffraction, low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED).

Neutron diffraction:

• Neutron diffraction or elastic neutron scattering is the application of neutron scattering to determine the atomic and/or magnetic structure of a material.

• A sample to be studied is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern. The obtained patterns provide information of structure of the material.

• This technique is similar to X-ray diffraction but due to their different scattering properties, neutrons and X-rays provide complementary information.

History:

• In 1932, neutron was first discovered by J. Chadwick

• In 1936, W. Elsasser proposed the idea of neutron scattering by crystalline materials.

• In 1936, F. Bloch predicted the feasibility of neutron scattering by magnetic moment in condensed materials.

• In 1940s and 1950s, high flux neutron reactor sources were built in U. S. and Canada (Chalk River's NRX reactor, ORNL's graphite reactor). In 1956, B. Brockhouse built the first triple-axis spectrometer in Chalk River Laboratory

E. Wollan and C. Shull did a lot of pioneering work in modern neutron diffraction between 1948 and 1955.

• 1994, the Nobel Prize