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MS213 Crystallography and Diffraction

MS213 Crystallography and Diffraction. Crystal Structure: Cubic System (BCC, FCC). Soon Ho Kwon Computational Materials Science lab. KAIST honest@kaist.ac.kr. 09/11/2013. What is crystal?.

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MS213 Crystallography and Diffraction

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  1. MS213 Crystallography and Diffraction Crystal Structure: Cubic System (BCC, FCC) Soon Ho Kwon Computational Materials Science lab. KAIST honest@kaist.ac.kr 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. Nature432 488 (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". Alattice is a set of points, regularly arranged in space, for which the environment of each point is identical. c α β b γ a crystal lattice http://www.materials.ac.uk/elearning/matter/Crystallography/3dCrystallography/

  4. 4 Types of Unit Cell P = Primitive I = Body-centered F = Face-centered C = Side-centered + 7 Crystal System → 14 Bravais Lattice 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% FCC BCC Simple cubic http://www.youtube.com/watch?v=GEMw0CKV4qw

  6. Diamond structure 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 !

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