Diatomic chain - acoustic modes
Longitudinal acoustical vibrations
Long wavelength vibration (k<<π/a)
Medium wavelength vibration (k~0.5π/a)
Zone-edge vibration (k=π/a)
Transverse acoustical vibrations
Long wavelength vibration (k<<π/a)
Medium wavelength vibration (k~0.5π/a)
Zone-edge vibration (k=π/a)