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In crystallography, **crystal structure** is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material.^{[1]} Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter.

The smallest group of particles in material that constitutes this repeating pattern is unit cell of the structure. The unit cell completely reflects symmetry and structure of the entire crystal, which is built up by repetitive translation of unit cell along its principal axes. The translation vectors define the nodes of Bravais lattice.

The lengths of principal axes/edges, of unit cell and angles between them are lattice constants, also called *lattice parameters* or *cell parameters*. The symmetry properties of crystal are described byconcept of space groups.^{[1]} All possible symmetric arrangements of particles in three-dimensional space may be described by 230 space groups.

The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency.

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^{a}^{b}Hook, J.R.; Hall, H.E. (2010).*Solid State Physics*. Manchester Physics Series (2nd ed.). John Wiley & Sons. ISBN 9780471928041.