MAT_101_Summer08Lecture_3

MAT_101_Summer08Lecture_3 - INTERATOMIC POTENTIALS r r...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
1 INTERATOMIC POTENTIALS Molecule Two atoms r r Bond length , r Bond energy , E o F r Melting Temperature , T m E o = “bond energy” Energy (r) r o r unstretched length larger T m smaller T m Energy (r) r o T m is larger if E o is larger. PROPERTIES FROM BONDING: T M
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 Elastic modulus , E • E ~ curvature at r o cross sectional area A o L length, L o F undeformed deformed L F A o = E L o Elastic modulus r larger Elastic Modulus smaller Elastic Modulus Energy r o unstretched length E is larger if E o is larger. PROPERTIES FROM BONDING: E Coefficient of thermal expansion , α α ~ symmetry at r o α is larger if E o is smaller. length, L o unheated, T 1 heated, T 2 = α ( T 2 - T 1 ) L o coeff. thermal expansion smaller α larger α Energy r o PROPERTIES FROM BONDING: α
Background image of page 2
3 Ceramics (Ionic & covalent bonding): Metals (Metallic bonding): Polymers (Covalent & Secondary): secondary bonding Large bond energy large T m large E small α Variable bond energy moderate T m moderate E moderate α Directional Properties Secondary bonding dominates small T small E large α SUMMARY: PRIMARY BONDS ISSUES TO ADDRESS. .. • How do atoms assemble into solid structures? (for now, focus on metals) • How does the density of a material depend on its structure? • When do material properties vary with the sample (i.e., part) orientation? CHAPTER 3: CRYSTAL STRUCTURES & PROPERTIES
Background image of page 3

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

View Full DocumentRight Arrow Icon
4 • Non dense, random packing •Dense , regular packing Dense, regular-packed structures tend to have lower energy. Energy r typical neighbor bond length typical neighbor bond energy Energy r typical neighbor bond length typical neighbor bond energy ENERGY AND PACKING 1 nm TEM Image of Sc 2 O 3 (S. Stemmer) CRYSTALLINE MATERIALS AFM image of Au surface
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 13

MAT_101_Summer08Lecture_3 - INTERATOMIC POTENTIALS r r...

This preview shows document pages 1 - 5. Sign up to view the full document.

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