Kriistallide

Kriistallide is the Estonian term for crystals, referring to solid substances in which the atoms are arranged in a highly ordered, repeating lattice that extends in three dimensions. This arrangement gives crystals distinct external faces and precise internal structure.

Crystals are characterized by long-range order and specific symmetry. They exhibit anisotropic properties, meaning that physical properties such as refractive index, hardness, and cleavage can vary with direction. Crystal systems group crystals by their lattice symmetries (for example, cubic, tetragonal, hexagonal).

Formation: Crystallization occurs when a liquid, melt, or solution becomes supersaturated or when a solid phase transforms, allowing atoms or molecules to arrange into a lattice. Growth by addition of units on existing faces produces well-formed crystals, while rapid growth or impurities can lead to imperfect shapes called polycrystals.

Classification and examples: Natural kriistallide are minerals with a defined chemical composition, such as quartz (SiO2), halite (NaCl), and calcite (CaCO3). Synthetic kriistallide include semiconductor silicon and lithium niobate used in optics; many crystals are valued as gemstones (diamond, ruby, emerald).

Uses and significance: Crystals underpin electronics, optics, and catalysis; they also provide insight into geological history through mineralogy and crystallography. Understanding crystal structures informs material science, chemistry, and earth science.

History and methods: The study of crystals advanced with the development of X-ray crystallography in the early 20th century, enabling determination of atomic arrangements. Modern techniques include electron diffraction and neutron scattering.