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In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals. There are three main varieties of these crystals: *Primitive cubic (abbreviated ''cP''〔International Tables for Crystallography (2006). Vol. A, Section 2.1.3, pp. 14–16. (Link )〕 and alternatively called ''simple cubic'') *Body-centered cubic (abbreviated ''cI''〔 or ''bcc''), *Face-centered cubic (abbreviated ''cF''〔 or ''fcc'', and alternatively called ''cubic close-packed'' or ''ccp'') Each is subdivided into other variants listed below. Note that although the ''unit cell'' in these crystals is conventionally taken to be a cube, the ''primitive'' unit cell often is not. This is related to the fact that in most cubic crystal systems, there is more than one atom per cubic unit cell. A classic isometric crystal has square or pentagonal faces. ==Cubic space groups== The three Bravais lattices which form cubic crystal systems are: The primitive cubic system (cP) consists of one lattice point on each corner of the cube. Each atom at a lattice point is then shared equally between eight adjacent cubes, and the unit cell therefore contains in total one atom ( × 8). The body-centered cubic system (cI) has one lattice point in the center of the unit cell in addition to the eight corner points. It has a net total of 2 lattice points per unit cell ( × 8 + 1). The face-centered cubic system (cF) has lattice points on the faces of the cube, that each gives exactly one half contribution, in addition to the corner lattice points, giving a total of 4 lattice points per unit cell ( × 8 from the corners plus × 6 from the faces). Each sphere in an fcc lattice has coordination number 12. The face-centered cubic system is closely related to the hexagonal close packed (HCP) system, and the two systems differ only in the relative placements of their hexagonal layers. The () plane of a face-centered cubic system is a hexagonal grid. Attempting to create a C-centered cubic crystal system (i.e., putting an extra lattice point in the center of each horizontal face) would result in a simple tetragonal Bravais lattice. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cubic crystal system」の詳細全文を読む スポンサード リンク
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