Lecture 4: Diatomic Chain

We discuss generalities of phonon spectra. These include: frequency goes to zero at the reciprocal lattice vectors; group velocity goes to zero at the zone edge; frequency goes linear in k for small frequency; all physical modes are contained in the first Brillouin zone. We derive the dispersion relation for a linear chain of 2 distinct atom types. We discuss the quantization of phonons, and embark on a lightning fast review of the harmonic oscillator. A great java app showing how the harmonic oscillator eigenstates actually connect back to oscillatory motion is at:
http://www.fi.uib.no/AMOS/MOV/HO/

Audio