1. Crystal Structure: Cubic System (BCC, FCC)
MS213
Crystallography and Diffraction
Crystal Structure: Cubic System
(BCC, FCC)
Soon Ho Kwon
Computational Materials Science lab.
KAIST
09/11/2013

2. What is crystal?
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 (2004)

3. 7 crystal systems
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. a b c α β γ
crystal
lattice

4. 14 Bravais lattice 4 Types of Unit Cell + 7 Crystal System
P = Primitive
I = Body-centered
F = Face-centered
C = Side-centered +
7 Crystal System
→ 14 Bravais Lattice

5. Cubic system Cubic system: a=b=c and α=β=γ=90° Simple cubic: P, CN=6
Body Centered Cubic (BCC): I, CN=8, APF = 68%
Face Centered Cubic (FCC) : F, CN=12, APF = 74%
Simple cubic
BCC
FCC

6. Diamond structure Cf.) Zinc blend structure Tetrahedral bonding !
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).
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
Tetrahedral bonding !