Festkörpern

Festkörpern, or solids, constitute one of the fundamental states of matter in physics. They are characterized by a definite shape and volume, arising from strong interparticle forces that keep constituent atoms, ions, or molecules in fixed positions. At the microscopic level, matter in the solid state can be arranged in an ordered crystal lattice (crystalline solids) or in a disordered arrangement lacking long-range periodicity (amorphous solids).

Crystalline solids feature long-range order described by unit cells and Bravais lattices; examples include metals, salts, and minerals. Amorphous solids such as glasses have short-range order but no periodic lattice. Some solids are polycrystalline, consisting of many small crystallites with random orientations.

Key properties include rigidity and high density; mechanical behavior is captured by elastic moduli; crystals show anisotropy in properties along different directions. Thermal and electrical properties vary with bonding: metallic solids conduct electricity well; many ionic and covalent solids are insulators or semiconductors; band structure concepts explain conductivity in solids.

Defects such as vacancies, interstitials, dislocations, and grain boundaries influence strength, diffusion, and failure. Thermal history and processing conditions affect microstructure and properties.

Representative classes of Festkörpern include metallic solids, ionic solids, covalent-network solids (e.g., diamonds, silica), molecular solids (e.g., ice, solid CO2), and polymers. They are produced and processed by solidification, annealing, sintering, deposition, extrusion, and molding, among other methods. Understanding their structure–property relationships is central to materials science and engineering.