X-rays are used in X-ray diffraction (XRD) to study the arrangement of atoms in crystalline materials. When a crystal is exposed to a beam of monochromatic X-rays, the electrons in the atoms scatter the X-rays in specific directions. Because the atoms in a crystal are arranged in a regular repeating pattern, the scattered waves can interfere constructively at certain angles, producing a pattern of intense spots called diffraction peaks.
The relationship between the diffraction angles and the spacing of the crystal planes is given by Bragg’s Law.
By measuring the angles and intensities of the diffracted beams, scientists can:
- Determine crystal structure (unit cell size, shape, and symmetry).
- Identify unknown materials by comparing diffraction patterns to reference databases.
- Measure lattice parameters and detect structural defects.
- Study phase changes in materials under varying temperature or pressure.
In short, X-rays in XRD act like an atomic-scale ruler, allowing researchers to “see” the arrangement of atoms without destroying the sample.