PHY460 F2006 Lecture Notes 2

(pdf - 6 slides/page lect 2 -- lect 2a)
Monday, August 28, 2006
Lecturer: Richard Martin

Homework 1

Reading:
Kittel, Chapt. 1

Structure of Crystals

A Crystal is a Periodic Array of (Groups of) Atoms
Crystal Structure = Lattice + Basis
- Lattice = set of translations
  - Lattice points need not be at atom sites
  - Anything that repeats; Escher Drawings
  - Lattice of translations
- Basis = set of atoms associated with each lattice point
  - Single atom in simple elemental crystal
  - Pair of atoms in crystal like NaCl
  - Molecule(s) in molecular crystal
- Primitive Unit Cell
  - Smallest repeat cell
  - Not unique, but all have same volume
Properties of the Lattice
- Lattice types in two dimensions
- Lattice types in three dimensions
  - Body Centered Cubic
  - Face Centered Cubic (cubic close packed)
- Lattice planes
Examples of Crystals
- NaCl
- CsCl
- diamond (C, Si, Ge)
- hexagonal close packed

Last Modified Aug. 27
Email question/comments/corrections to rmartin@uiuc.edu .