lecture3 - Chapter Chapter 3 1 The Structure of Crystalline...

Info iconThis preview shows pages 1–14. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter Chapter 3 1 The Structure of Crystalline Solids The Structure of Crystalline Solids ISSUES TO ADDRESS... • How do atoms assemble into solid structures? (for now, focus on metals) The The Structure of Crystalline Solids Structure of Crystalline Solids 2 • How does the density of a material depend on its structure? • When do material properties vary with the orientation in a crystal? (Isotropic vs. anisotropic)? • Non dense, random packing Energy and Packing Energy and Packing Energy r typical neighbor bond length typical neighbor bond energy 3 • Dense, ordered packing Dense, ordered packed structures tend to have lower energies, i.e. thermodynamically more stable Energy r typical neighbor bond length typical neighbor bond energy • atoms pack in periodic, 3D arrays Crystalline materials...-metals-many ceramics-some polymers crystalline SiO 2 Materials and Packing Materials and Packing • typical of: 4 • atoms have no periodic packing Noncrystalline materials...-complex structures-rapid cooling noncrystalline SiO 2 " Amorphous " = Noncrystalline Si Oxygen • occurs for: Metallic Metallic Crystal Structures Crystal Structures • How can we stack metal atoms to minimize empty space? 2-dimensions 5 vs. Now stack these 2-D layers to make 3-D structures Crystal Crystal Systems Systems 7 crystal systems Unit cell: smallest repetitive volume which contains the complete lattice pattern of a crystal. 6 14 crystal lattices (Bravais lattices) a, b, and c are the lattice constants The 14 The 14 Bravais Bravais Lattices Lattices 7 Courtesy of P. Davies (UPenn) Crystal Class Axes Designation Cubic a=a 1 =a 2 =a 3 α= β = γ =90 o Tetragonal a=a 1 =a 2 ; c=a 3 ; a ≠ c α= β = γ =90 o Orthorhombic a=a 1 ≠ b= a 2 ≠ c=a 3 α= β = γ =90 o Symm The 14 The 14 Bravais Bravais Lattices Lattices 8 Hexagonal a=a 1 =a 2 ≠ c=a 3 α= β =90 o ; γ =120 o Rhombohedral a=a 1 =a 2 =a 3 α ≠ 90 o ; β = γ =90 o Monoclinic a=a 1 ≠ b= a 2 ≠ c=a 3 α ≠ 90 o ; β = γ =90 o Triclinic a=a 1 ≠ b= a 2 ≠ c=a 3 α ≠ 90 o ; β≠ 90 o ; γ≠ 90 o α ≠ β≠ γ≠ 90 o etry ↓ Courtesy of Encyclopaedia Britannica CsCl & NaCl Structures CsCl NaCl YBCO Superconductor Structure Orthorhombic unit cell! Diamond and ZnS Structures Diamond ZnS ZrO 2 (Fluorite) Lattice • Tend to be densely packed. • Reasons for dense packing:- Typically, only one element is present, so all atomic radii are the same.- Metallic bonding is not directional. Metallic Crystal Structures Metallic Crystal Structures 13- Nearest neighbor distances tend to be small in order to lower bond energy.- Electron cloud shields cores from each other • Have the simplest crystal structures....
View Full Document

This note was uploaded on 02/08/2011 for the course GENERAL EN 407 taught by Professor Akdogan during the Fall '10 term at Rutgers.

Page1 / 70

lecture3 - Chapter Chapter 3 1 The Structure of Crystalline...

This preview shows document pages 1 - 14. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online