Numerical simulation techniques were used to study the vibrational properties of random networks. The networks, containing up to 1500 ions, were generated by the introduction of a large number of defects in regular crystals. Periodic boundary conditions were imposed. Long-range Coulomb effects were included for the first time. Our simulations reveal the existence of long-wavelength optic-type excitations which exhibit LO-TO splitting similar to crystalline solids. The LO-mode has a negative dispersion, whereas almost no dispersion is observed for the TO-mode. In the density of states, the TO-mode shows up as a peak, whereas the LO-mode defines the high frequency band edge.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry