On the velocity dependence of the dislocation drag coefficient from phonon wind

Technical Report · Tue May 29 00:00:00 EDT 2018

DOI:https://doi.org/10.2172/1434423· OSTI ID:1434423

Blaschke, Daniel N.  ^[1]; Mottola, Emil  ^[1]; Preston, Dean Laverne ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

The phonon wind mechanism, that is, the anharmonic interaction and scattering of phonons by a moving dislocation, imparts a drag force B (v,T,ρ) v on the dislocation. The drag coefficient B has been previously computed and experimentally determined only for dislocation velocities v much less than transverse sound speed, c_T. In this paper we derive an expression for the velocity dependence of B up to c_T in terms of the third-order elastic constants of the crystal. We compute the velocity dependence of the phonon wind contribution to B in the range 1%–90% c T for Al, Cu, Fe, and Nb in the isotropic Debye approximation, and to better accuracy than in earlier studies. It is proved that the drag coefficient for screw dislocations scattering transverse phonons is finite as v → c_T, whereas B is divergent for edge dislocations scattering transverse phonons in the same limit. We compare our results to experimental results wherever possible and identify ways to validate and further improve the theory with more realistic phonon dispersion relations, MD simulations, and more accurate measurements.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1434423
• Report Number(s): LA-UR-16-24559
• Country of Publication: United States
• Language: English