Bonding in Solids
Physics 215 Winter 2002
Introduction to Modern Physics
Prof. Ioan Kosztin Lecture #23
Solid State Physics
• Bonding in solids (metals, isolators, semiconductors) • Classical free electron theory of metals • Quantum theory of metals • Band theory of solids • Semiconductors • Lasers
Classification of solids
• Phases of matter: • solid (well defined shape and volume) • liquid (only well defined volume) • gas (no defined shape or volume) • plasma (an overall neutral collection of charged and neutral particles) • Solids • crystalline (atoms form a regular periodic structure) • amorphous (atoms have irregular spatial distribution) • Solids • metals (good electrical/heat conductors) • semiconductors • insulators (poor electrical/heat conductors)
Bonding in solids: Ionic solids
Ionic solid crystals (e.g. NaCl) are held together by the Coulomb attractive interaction between ions with opposite sign (ionic bonding)
e2 b U = −αk + m r r
(α = 1.7476 for Na +Cl − )
(m ~ 10) k = 1 / 4πε 0
Madelung constant
Ionic cohesive energy:
11 U0 = min U (r ) = −αk 1 − m r0 mb r0 = αk
1 m −1
Bonding in solids: Ionic solids
Properties of ionic solid crystals: • relatively stable and hard • poor electrical/heat conductors • high melting/boiling temperatures • transparent to visible light • strong IR absorption • soluble in polar solvents (e.g., water)
Bonding in solids: Covalent solids
Atoms in the crystal are held together by covalent bonding C atoms in diamond form a tetragonal crystal structure Properties of covalent crystals: • very hard and stable • high melting point • good insulators • do not absorb light • larger cohesive energies (~10 eV) than in ionic crystals
Bonding in solids: Metallic solids
Atoms in a metallic crystal are held together by the effective attractive electrostatic interaction mediated by the conduction (valence) electron gas (metallic bonding) Properties of metallic crystals: • smaller
Introduction to Modern Physics
Prof. Ioan Kosztin Lecture #23
Solid State Physics
• Bonding in solids (metals, isolators, semiconductors) • Classical free electron theory of metals • Quantum theory of metals • Band theory of solids • Semiconductors • Lasers
Classification of solids
• Phases of matter: • solid (well defined shape and volume) • liquid (only well defined volume) • gas (no defined shape or volume) • plasma (an overall neutral collection of charged and neutral particles) • Solids • crystalline (atoms form a regular periodic structure) • amorphous (atoms have irregular spatial distribution) • Solids • metals (good electrical/heat conductors) • semiconductors • insulators (poor electrical/heat conductors)
Bonding in solids: Ionic solids
Ionic solid crystals (e.g. NaCl) are held together by the Coulomb attractive interaction between ions with opposite sign (ionic bonding)
e2 b U = −αk + m r r
(α = 1.7476 for Na +Cl − )
(m ~ 10) k = 1 / 4πε 0
Madelung constant
Ionic cohesive energy:
11 U0 = min U (r ) = −αk 1 − m r0 mb r0 = αk
1 m −1
Bonding in solids: Ionic solids
Properties of ionic solid crystals: • relatively stable and hard • poor electrical/heat conductors • high melting/boiling temperatures • transparent to visible light • strong IR absorption • soluble in polar solvents (e.g., water)
Bonding in solids: Covalent solids
Atoms in the crystal are held together by covalent bonding C atoms in diamond form a tetragonal crystal structure Properties of covalent crystals: • very hard and stable • high melting point • good insulators • do not absorb light • larger cohesive energies (~10 eV) than in ionic crystals
Bonding in solids: Metallic solids
Atoms in a metallic crystal are held together by the effective attractive electrostatic interaction mediated by the conduction (valence) electron gas (metallic bonding) Properties of metallic crystals: • smaller