Diffraction

Background

Crystalline, polycrystalline and amorphous materials.

The crystal lattice: unit cell and point lattices. The seven crystal systems. Space groups. Miller indices and Unit vectors. Reciprocal space.

Some diffraction properties and conditions

• Elastic scattering (no energy loss).
• The wavelength of the radiation should be comparable to the interatomic spacing of the material.

Bragg's law

• Condition: The planes of atoms responsible for a diffraction peak have to behave as a specula mirror, so that the angle of incidence \theta equals the angle of reflection.
• Bragg's law (her kan noen skriv

<math> n\lambda=2dsin\theta </math>

• Allowed and forbidden reflections.