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Generalised Viscosity and Dislocation Damping Constant in Diatomic Crystalline Solids
Author(s) -
Martin J. W.,
Paetsch R.
Publication year - 1976
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220740238
Subject(s) - debye model , debye , phonon , anharmonicity , thermoelastic damping , condensed matter physics , dislocation , physics , grüneisen parameter , constant (computer programming) , viscosity , thermodynamics , thermal expansion , thermal , computer science , programming language
Using Brailsford's model for the anharmonic dislocation drag, generalized viscosities and the damping constant have been calculated for a diatomic solid, represented by a modified Debye‐Einstein type phonon spectrum. The generalized viscosity and its temperature dependence have been examined in detail. It is shown that the effect of phonon dispersion is to increase the region in which the thermoelastic effect makes an appreciable contribution to the viscosity. Consequently, the dislocation drag constant for the Debye‐Einstein model is found to be enhanced by a factor \documentclass{article}\pagestyle{empty}\begin{document}$ \frac{1}{2}q_D l_A $\end{document} compared with the Debye model ( q D is the Debye wave number, l A the mean free path of the acoustic phonons). It is also shown that in general the damping constant is very sensitive to temperature, shape of phonon spectrum and phonon lifetimes and it is difficult to predict its temperature dependence. The Debye‐Einstein model gives B α T m , where m < 1 for intermediate temperatures and tends to one for high temperatures.