röntgendiffraction

Röntgendiffraction, commonly known as X-ray diffraction (XRD), is a set of techniques used to study the arrangement of atoms in crystalline materials by analyzing the pattern produced when X-rays scatter from the crystal lattice. X-ray wavelengths are comparable to interatomic spacings, making diffraction highly sensitive to crystal structure.

When X-rays strike a crystal, waves scattered by lattice planes interfere constructively at specific angles. For planes separated by distance d, Bragg's law describes the condition for constructive interference: nλ = 2d sin θ, where λ is the X-ray wavelength, θ the glancing angle, and n an integer. The resulting diffraction pattern, consisting of peaks at characteristic angles and intensities, contains information about lattice spacings and the arrangement of atoms within the unit cell.

Historically, X-ray diffraction emerged with Max von Laue's demonstration of crystal diffraction in 1912, followed by the Bragg brothers’ development of Bragg's law and its use in solving crystal structures in 1913. XRD measurements can be performed on powdered samples (powder diffraction), single crystals (single-crystal diffraction), or thin films and other geometries (Laue methods).

Modern XRD instruments use X-ray tubes or synchrotron sources and detectors such as scintillation counters or CCDs. Data analysis ranges from qualitative phase identification to quantitative lattice parameter determination and, with appropriate models, full crystal structure solutions. Powder patterns are often refined by methods like Rietveld refinement to extract detailed structural information.

Applications span materials science, chemistry, geology, metallurgy, semiconductors, and biology, including phase analysis, determination of crystal structures, residual stress assessment, texture, and film characterization. Limitations include the need for crystallinity and sample quality, while safety considerations address ionizing radiation exposure.