L11SimpCrStruc145s10

# L11SimpCrStruc145s10 - Lecture 11: Basic Crystal Structures...

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Lecture 11, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Reading assignment : C&R §3.1-3.5; §3.9; §3.16; OGC §21.2 Learning objectives: Know characteristics of several simple crystal structures Body centered cubic Face-centered cubic (cubic close-packed) Hexagonal close-packed Diamond cubic Know how to compute atomic packing factor Lecture 11: Basic Crystal Structures 1

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Lecture 11, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Body-Centered Cubic (BCC) [OGC § 21.2] In BCC structure, all atoms are the same element (different colors are used here for visual clarity) Every atom has 8 nearest neighbors Coordinates occupied: Total of 2 atoms per unit cell: OGC Figure 21.12 2
Lecture 11, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Body-Centered Cubic (BCC) [OGC § 21.2] Movie from “Visualizations in Materials Science,” Prof. John C. Russ, North Carolina State University 3

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Lecture 11, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Atomic packing factor Relationship between atomic radius r and lattice parameter a : Volume of atoms: Volume of cubic cell: Atomic packing factor: 4 3 r a = V atoms = 2 4 π r 3 3 = 3 8 a 3 V cell = a 3 APF = V atoms V cell = 3 8 = 0.68 Body-Centered Cubic (BCC) [C&R §3.4] C&R Figure 3.2 4
5 Lecture 11, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Face-Centered Cubic (FCC) [OGC § 21.2] Coordinates occupied: Total of 4 atoms per unit cell: A.k.a.

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## This note was uploaded on 01/30/2011 for the course EMSE 103 taught by Professor Ggh during the Spring '10 term at Case Western.

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L11SimpCrStruc145s10 - Lecture 11: Basic Crystal Structures...

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