Local order and long-range order
Short-range order and long-range order describe order aspects of the arrangement of atoms or molecules in liquids and solids . Such considerations are particularly relevant in physical chemistry and crystallography or solid state physics . While the short-range order relates to the spatial arrangement of the next, perhaps the next but one, particle of the substance, a long-range order requires a repetitive arrangement of the particles over numerous repetitions.
Local order
Short-range order is a regular grouping of particles only in the vicinity of a reference particle. However, with distance, the order can decrease, for example for a molecule in a liquid or an atom in an amorphous solid . The bond lengths and angles to the nearest neighbors are mainly used to describe the order .
We find the ideal case of a pure short-range order in liquids in which the particle distances ( atomic or molecular distances) are constant and the bond angles fluctuate strongly. There is almost no correlation of the bond angles with the next but one neighbor .
The entire spectrum of materials between pure short-range order and long-range order occurs in nature.
Long-range order
As long-range order is called the regular and periodic arrangement ( "to the distance") of molecules or atoms in a crystalline solid state , in particular in intermetallic phases .
Solids without long-range order are called amorphous solids such as glass and supercooled melt. Like liquids, they only have a short-range order.
The structure of real crystals deviates from an ideal long-range order in many places. Real crystals - also called crystallites - contain a large number of crystal defects without losing their long-range order character.
States of order in solids
| Status | Range of order | example |
|---|---|---|
| amorphous (local order) | next and next but one particle | Glass |
| nanocrystalline | Nanometer | Paracrystal |
| micro crystalline | Micrometer | quartz |
| polycrystalline | millimeter | Polycrystalline diamond |
| monocrystalline (long-range order) | centimeter | monocrystalline ingots |
Individual evidence
- ↑ Ludwig Bergmann, Rainer Kassing, Clemens Schaefer, with Stefan Blügel: 6. Textbook of Experimental Physics solids . Walter de Gruyter, 2005, ISBN 978-3-11-017485-4 , p. 691.