Kristallografiaa

Kristallografiaa, commonly referred to as crystallography, is the science that studies the arrangement of atoms in crystalline materials and the methods used to determine these structures. It connects chemistry, physics, and materials science to understand how atoms pack in regular lattices and how this arrangement governs properties such as strength, conductivity, and optical behavior.

Historically, the field emerged from X-ray diffraction experiments in the early 20th century. In 1912, Max von Laue showed that crystals diffract X-rays, proving that atoms are arranged in periodic arrays. In 1913, William Lawrence Bragg and his father William Henry Bragg formulated Bragg's law, which relates diffraction angles to lattice spacings and enables the calculation of crystal structures.

X-ray crystallography is the primary tool for determining atomic structures. Other diffraction-based methods include neutron diffraction, which is sensitive to light atoms and magnetic order, and electron diffraction, useful for very small crystals. Powder diffraction can analyze polycrystalline samples, whereas single-crystal data provide higher resolution. In recent decades, cryo-electron microscopy has complemented crystallography for biological macromolecules that are difficult to crystallize.

Data from diffraction patterns are translated into electron density or nuclear density maps by mathematical phase retrieval, often using Fourier synthesis. The phase problem is addressed by direct methods, Patterson methods, or molecular replacement, followed by refinement to improve model fit and to estimate errors. Validation includes R factors, geometric checks, and consistency with other data.

Applications of crystallography span chemistry, biochemistry, materials science, and geology. It underpins drug design by revealing binding sites, guides the development of new alloys, and informs mineral identification. Landmark achievements include solving the structures of proteins and nucleic acids, which has transformed life sciences.