𝔖 Bobbio Scriptorium
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Transport and vibrational lifetimes in amorphous structures

✍ Scribed by R. Orbach


Book ID
103941259
Publisher
Elsevier Science
Year
1996
Tongue
English
Weight
287 KB
Volume
219-220
Category
Article
ISSN
0921-4526

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✦ Synopsis


The lifetimes of high energy lattice vibrational states in amorphous or glassy materials are calculated on the basis of vibrational localization for energies co > ~oc, where o2c signifies the mobility edge. Anharmonicity-induced localized vibrational state hopping, with the emission of an extended vibrational state (a phonon), is found to be the dominant decay mechanism. Because of the contribution of the same vertex to thermal transport via localized vibrational state hopping, the vibrational lifetimes can be expressed in terms of this hopping contribution to the thermal conductivity, with only COc as an undetermined variable. At low temperatures, the high energy vibrational lifetime is found to be proportional to the exponential of (o)/~oc)d'~'D where dΒ’ is the superlocalization exponent of the localized vibrational state, and D is the mass density scaling exponent (equal to the Euclidean dimension d for dense systems, and the fractal dimension for fractal systems). Excellent numerical agreement is found with the experiments of Scholten et al. which find a lifetime r : 70 ns for the 480 cm-1 TO vibration in a-Si : H.


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