Summary STRUCTURE OF CRYSTALLINE SOLIDS

STRUCTURE OF CRYSTALLINE
SOLIDS



Structure of
1 Crystalline Solids

,Atomic Arrangement
• Crystalline : orderly : all metals and many ceramics
• Amorphous : random : most polymers
• Semi-crystalline: mixture : mostly polymers

Short-Range Order versus Long-Range Order
• Short-range order (SRO) - The regular and predictable
arrangement of the atoms over a short distance - usually
one or two atom spacings.

• Long-range order (LRO) - A regular repetitive
arrangement of atoms in a solid which extends over a
very large distance.


Structure of
2 Crystalline Solids

, The levels of atomic
arrangement in materials.
(a) Inert gases have no
regular order of atoms. (b)
and (c) Some materials,
such as steam and glass,
have ordering only over a
short distance. (d) Metals
and other solids have a
regular ordering of atoms
that extends through the
materials.




Structure of
3 Crystalline Solids

, Crystalline versus Non-crystalline Materials

In crystalline materials...
• atoms pack in periodic, 3D arrays
• typical of: - metals
- many ceramics
- some polymers
crystalline SiO2

Si Oxygen
In non-crystalline materials...
• atoms have no periodic packing
- complex structures
• occurs for:
- rapid cooling


"Amorphous" = Non-crystalline
non-crystalline SiO2

Structure of
4 Crystalline Solids