X-ray Diffraction (XRD)






Basic Theory: Diffraction and Bragg's Law

X-ray Diffraction and Bragg’s Law

X-rays have wavelengths on the order of a few angstroms (1 Angstrom = 0.1 nm).  This is the typical inter-atomic distance in crystalline solids, making X-rays the correct order of magnitude for diffraction of atoms of crystalline materials. 

How are Diffractions Patterns Made?

When X-rays are scattered from a crystalline solid they can constructively interfere, producing a diffracted beam.   What does this mean?

Constructive vs. Destructive Interference

Interference occurs among the waves scattered by the atoms when crystalline solids are exposed to X-rays.  There are two types of interference depending on how the waves overlap one another.

Constructive interference occurs when the waves are moving in phase with each other. Destructive interference occurs when the waves are out of phase.

This constructive interference results in diffraction patterns. 

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Celeste Morris, Bradley Sieve and Heather Bullen, Department of Chemistry, Northern Kentucky University, Highland Heights, KY 41099