Crystal
A crystal or crystalline solid is a solid material whose constituents, such as atoms, molecules or ions, are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations.
The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The word crystal is derived from the Ancient Greek word κρύσταλλος (krustallos), meaning both “ice” and “rock crystal”, from κρύος (kruos), "icy cold, frost".
Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks, ceramics, and ice. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass, wax, and many plastics.
Crystal (disambiguation)
Crystal is a form of matter significant in chemistry and mineralogy.
Crystal may also refer to:
Companies and brands
Places
People
Physical sciences
Crystal (software)
CRYSTAL is a quantum chemistry ab initio program, designed primarily for calculations on crystals (3 dimensions), slabs (2 dimensions) and polymers (1 dimension) using translational symmetry, but it can also be used for single molecules. It is written by V.R. Saunders, R. Dovesi, C. Roetti, R. Orlando, C.M. Zicovich-Wilson, N.M. Harrison, K. Doll, B. Civalleri, I.J. Bush, Ph. D’Arco, and M. Llunell from Theoretical Chemistry Group at the University of Torino and the Computational Materials Science Group at the Daresbury Laboratory near Warrington in Cheshire, England. The current version is CRYSTAL14, released in June 2014. Earlier versions were CRYSTAL88, CRYSTAL92, CRYSTAL95, CRYSTAL98, CRYSTAL03, CRYSTAL06, and CRYSTAL09.
Features
Hamiltonians
- Restricted
- Unrestricted
- Local functionals [L] and gradient-corrected functionals [G]
- Slater (LDA) [L]
- von Barth-Hedin (VBH) [L]
- Becke '88 (BECKE) [G]
- Perdew-Wang '91 (PWGGA) [G]
- Perdew-Burke-Ernzerhof (PBE) [G]
- Revised PBE functional for solids (PBEsol) [G]
- Second-order expansion GGA for solids (SOGGA) [G]
- Wu-Cohen '06 (WCGGA) [G]
