Crystalline materials (mainly metals and alloys, but also stoichiometric salts and other materials) are made up of solid regions of ordered matter (atoms placed in one of a number of ordered formations called Bravais lattices). These regions are known as crystals. A perfect crystal is one that contains no point, linear, or planar imperfections. There are a wide variety of crystallographic defects.
The hypothetical concept of a perfect crystal is important in the basic formulation of the laws of thermodynamics.
In crystallography, the phrase 'perfect crystal' can be used to mean "no line or planar defects", as it is difficult to measure small quantities of point defects in an otherwise defect-free crystal.
, a crystal structure is a unique arrangement of atoms in a crystalcrystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions.
Crystals are often naturally anisotropic, and in some media (such as liquid crystals) it is possible to induce anisotropy by applying e.
The space group of the crystal structure is composed of the translational symmetries in addition to the symmetries of the point group.
A crystal structure is composed of a unit cell, a set of atoms arranged in a particular way; which is periodically repeated in three dimensions on a lattice.
A crystal's structure and symmetry play a role in determining many of its properties, such as cleavage, electronic band structure, and optical properties.
The crystal system is the point group of the lattice (the set of rotation and reflection symmetries which leave a lattice point fixed), not including the positions of the atoms in the unit cell.
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