Crystal System

crystal system

[¦krist·əl ′sis·təm]

(crystallography)

One of seven categories (cubic, hexagonal, tetragonal, trigonal, orthorhombic, monoclinic, and triclinic) into which a crystal may be classified according to the shape of the unit cell of its Bravais lattice, or according to the dominant symmetry elements of its crystal class.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Crystal System

 

any of the seven groups of crystals obtained when a classification is made according to the symmetry of the unit cell. A system is characterized by the ratios between the a, b, and c axes and by the angles α, β, and γ of the unit cell. The seven systems are cubic (a = b = c; α = β = γ = 90°), tetragonal (a = b ≠ c; α = β = γ = 90°), hexagonal (a = b ≠ c; α = β = 90°; γ = 120°), trigonal (a = b = c; α = β = γ ≠ 90°), orthorhombic (a ≠ b ≠ c; α = β = γ = 90°), mono-clinic (a ≠ b ≠ c; α = β = γ = 90°; β ≠ 90°), and triclinic (a ≠ b ≠ c; α ≠ β ≠ γ ≠ 90°). As the broadest classification of crystal symmetry, each crystal system includes several symmetry point groups and Bravais lattices.

REFERENCE

Popov, G. M., and I. I. Shafranovskii. Kristallografiia, 5th ed. Moscow, 1972.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.