triclinico

Triclinico, in crystallography, denotes the triclinic crystal system, the least symmetric of the seven crystal systems. The term derives from Greek, combining tri- meaning "three" and klinē meaning "angle."

Characterized by three unequal principal axes (a, b, c) and three unequal interaxial angles (α, β, γ), none of which is 90 degrees in the general case. As a result, the unit cell is oblique and lacks right angles.

Symmetry: Triclinic crystals possess the lowest possible symmetry. The applicable point groups are 1 and 1̅, and the lattice is typically primitive (P). Common space groups include P1 and P-1.

Consequences: The low symmetry leads to highly anisotropic physical properties, such as optical and mechanical anisotropy, and makes structural determination by X-ray diffraction more complex.

Examples: Minerals such as albite and anorthite (plagioclase feldspars) crystallize in the triclinic system; other triclinic minerals include certain zeolites and some organic crystals.

See also: Crystallography, Crystal system, Triclinic lattice.