SV MTE Metal Structures

SV MTE Metal Structures - Metallic Structures Fall 2010...

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Metallic Structures Fall 2010 Last revised 10/9/10 11:25 am
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Lecture Topics 3D Structures of Metals: FCC, HCP, BCC Close Packed planes, Coordination Numbers, Nearest Neighbors CP structures CP directions Theoretical Density Calculations
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Learning Objectives Be able to draw, describe, and distinguish the geometries of the three most common metallic crystal structures FCC HCP BCC Be able to calculate theoretical densities of metals, given unit cell parameters and atomic masses
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Two Models for Metals Partially filled Valence band (VB) Band Model + + + + + + + + + + + + + + + + Bond Model Electrons are delocalized Bonds are non-directional “sea of electrons”
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Metallic Bonding Model atoms are hard spheres. No overlap, no compression Metal atoms can bond at any angle because electrons are delocalized . Bonding is nondirectional . TPS: Using what you have learned from 2D circles, what is the bonding “strategy” for metals to reduce their overall energy?
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iClicker: Close Packed Planes What is the maximum number of bonds that one sphere can form in a plane? A. 4 B. 6 C. 8 D. 12 E. 14
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Vocabulary Coordination Number (CN) Nearest Neighbor (NN) Next Nearest Neighbor or 2 nd Nearest Neighbor
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Top View of One Layer of Close-packed Spheres
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An atom in a second layer has two possible places to sit 1 2
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The second layer (B) can go on either site 1 or 2 equivalently : 1 2 or
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SV MTE Metal Structures - Metallic Structures Fall 2010...

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