Unit Cell Of Crystal
Crystal structure refers to the specific arrangement of atoms in a crystal that, taken together, define the shape of a large piece of the crystal. For instance, salt – sodium chloride – is composed of a large atom and a small atom, and because of the size of its molecules and their strong polarity its crystal structure forms near perfect squares.
The smallest possible sample of atoms arranged three dimensionally in the unit structure of the crystal is called a unit cell. This unit cell, repeated infinitely on a three dimensional lattice, defines the ultimate structure of the crystal in symmetry and structure; it also defines secondary properties such as cleavage, electronic band structure, and optical properties like color and transluscence.
Unit cells are described by lattice parameters, lengths and angles of cell edges, and the precise positions of atoms in the unit cell described by atomic positions
(xi,yi,zi) as measured from a point on the lattice structure.
A unit cell is not the smallest possible unit of a crystal; for instance, in sodium chloride, a single sodium chloride molecule can be tiled to completely fill space in a lattice even though it does not make up the entirety of the crystal structure. This is called a primitive unit cell, distinct from a real unit cell by the fact that it lacks the symmetry.
Web Resources On Unit Cell Of Crystal
3-D Crystal Lattice Images
Unit Cell Dimensions
Book Resources On Unit Cell Of CrystalCrystal Structure Determination by Massa & Gould
Crystal Structure Determination by William Clegg
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