Krystallografia

Krystallografia is the branch of science that studies the arrangement of atoms in crystalline materials and uses this information to determine crystal structures. It combines ideas from physics, chemistry, and mathematics to describe how atoms repeat in three-dimensional space. The results of crystallography explain properties such as hardness, optics, and reactivity in solids.

Historically, key advances occurred in the early 20th century. Louis de Laue showed that crystals diffract X-rays in 1912, and William Henry Bragg and his son William Lawrence Bragg developed the practical approach of X-ray crystallography and Bragg's law, which relates diffraction to lattice spacing. These breakthroughs established crystallography as a central tool in chemistry and mineralogy.

X-ray crystallography remains the primary method. A crystal is irradiated with X-rays; the resulting diffraction pattern is analyzed to produce an electron density map from which atomic positions are inferred. Other methods include neutron diffraction, which is sensitive to light elements; and electron diffraction and electron crystallography for very small crystals. Powder diffraction is used when single crystals are unavailable.

Key concepts include the unit cell, lattice, and symmetry described by space groups. Data collection, indexing of reflections, and refinement against models seek to minimize agreement factors between observed and calculated patterns. The resolution of the data determines how precisely atomic positions can be located.

Applications span chemistry, biology, materials science, and geology. Crystallography revealed the structures of countless minerals, drug targets, enzymes, and the DNA double helix. It underpins structure-based drug design, catalyst development, and the study of crystalline materials such as metals and perovskites.

Modern crystallography often uses synchrotron light sources and advanced computer algorithms. Developments in cryo-crystallography and integrated approaches with cryo-electron microscopy have broadened the scope of structural science and enabled investigations of flexible or heterogeneous specimens.