Europhys. Lett, 47 (4), pp. 468-473 (1999)
Anharmonicity and thermal transport in network glasses
T. Nakayama 1 and R. Orbach 2
1 Department of Applied Physics,
Hokkaido University - Sapporo 060-8628, Japan
2 Department of Physics, University of California
Riverside, California 92521-0101, USA
(received 17 February 1999; accepted 18 June 1999)
PACS. 63.20Pw - Localized modes.
PACS. 63.50 - Vibrational states in disordered systems.
PACS. 66.70 - Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves.
The Nakayama model for network glasses classifies vibrational states into extended (ex), strongly localized (sl), and mesoscopically localized (ml), in increasing order of energy. Recently measured Raman spectra under hydrostatic pressure exhibit sl-mode anharmonicity at least twenty times that for the ex and ml modes. The ex modes can induce hopping of the sl modes, leading to a contribution to the thermal conductivity . This additional channel for heat conduction is consistent with measurements for a wide variety of glassy materials above the plateau temperature.
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