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MS213 Crystallography and Diffraction. Crystal Structure: Cubic System (BCC, FCC). Soon Ho Kwon Computational Materials Science lab. KAIST [email protected]. 09/11/2013. What is crystal?. - PowerPoint PPT Presentation
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MS213 Crystallography and Diffraction
09/11/2013
Crystal Structure: Cubic System (BCC, FCC)
Soon Ho KwonComputational Materials Science lab. [email protected]
A crystal or crystalline solid is a solid material, whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions.
Cf.) An "amorphous solid" is a solid in which there is no long-range order of the positions of the atoms.
Nature 432 488 (2004)
What is crystal?
The crystal system is a grouping of crystal structures that are categorized according to the axial system used to describe their "lattice". A lattice is a set of points, regularly arranged in space, for which the environment of each point is identical.
http://www.materials.ac.uk/elearning/matter/Crystallography/3dCrystallography/
a
b
c
αβ
γ
7 crystal sys-tems
latticecrystal
4 Types of Unit CellP = Primitive I = Body-centeredF = Face-centeredC = Side-centered+ 7 Crystal System
→ 14 Bravais Lattice
4 Types of Unit CellP = Primitive I = Body-centeredF = Face-centeredC = Side-centered+ 7 Crystal System
→ 14 Bravais Lattice
14 Bravais lat-tice
Cubic system: a=b=c and α=β=γ=90°
Simple cubic: P, CN=6Body Centered Cubic (BCC): I, CN=8, APF = 68%Face Centered Cubic (FCC) : F, CN=12, APF = 74%
Simple cubic BCC FCC
Cubic system
http://www.youtube.com/watch?v=GEMw0CKV4qw
It can be described as two interpenetrating FCC structures, one at co-ordinates (0,0,0) and the other at (1/4,1/4,1/4).
Tetrahedral bonding !
Cf.) Zinc blend structure
It has a cubic close packed (face centred) array of A and the B sit in tetrahedral (1/2 occupied) sites in the lattice
Diamond struc-ture