 |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
LINKS:
|
Lattice Constants
A crystal is a material that has an orderly and periodic arrangement of atoms in three-dimensional space. The repetitive arrangement of atoms in a crystal is called a lattice. The smallest volume in a lattice that represents one full repetition of its periodic atom arrangement is called a unit cell. The manner in which the atoms are arranged in a unit cell is known as its crystal structure. The crystal structure of the unit cell is always the same as that of a bigger chunk of the crystal, so a given bulk of crystal may be studied using just a small representative sample thereof.
The lengths of the edges of a unit cell along its major axes are known as lattice constants, which are usually denoted by three numbers, a, b, and c. In some crystal structures, however, the edge lengths along all axes are equal (a=b=c), so only one lattice constant is used for its dimensional description, a.
Lattice constant values and knowledge of crystal structure are needed to calculate distances between neighboring atoms in a crystal, as well as in determining some of the crystal's important physical and electrical properties. Note that, depending on the crystal structure, the distance between two neighboring atoms in a lattice may be less than the lattice constant. Table 1 shows the crystal structures and lattice constants of some semiconductors.
Table 1. Lattice Constants and Crystal Structures of some Semiconductors and Other Materials
Copyright
© 2004
www.SemiconFarEast.com.
All Rights Reserved. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||