Thermal conductivity of amorphous solids above the plateau: Molecular-dynamics study

The thermal conductivities of two-dimensional crystalline, amorphous, and quasicrystalline classical models are studied via the nonequilibrium molecular-dynamics method. The behavior of the high-temperature thermal conductivities of crystal and glasses are reproduced. The difference between the thermal conductivities of the crystalline and amorphous models is explained by the presence of localized vibrational modes found in the latter. The results support the model of anharmonicity-induced hopping heat transfer in glasses. The thermal conductivity of the quasicrystalline model does not differ from that of the amorphous model, suggesting that the effect of quasiperiodicity on the thermal conductivity is the same as that of a simple aperiodicity. It is shown that localized modes are at the origin of strong anharmonicity of amorphous solids. This anharmonicity, together with the localization, influences the spectral intensities, which have several peaks instead of one.