Crystal System (redirected from Bravais law)

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.

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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.