[SY-C8] Symposium C-8

[SY-C8] Thermal fluctuations of dislocations reveal the interplay between their core energy and long-range elasticity.

Invited

^○Pierre-Antoine Geslin^1,2,3, David Rodney⁴ (1.Mateis lab, INSA Lyon/CNRS, France, 2.Institute for Materials Research, Tohoku University, Japan, 3.Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Japan, 4.Institut Lumière Matière, Université Lyon 1, France)

Thermal fluctuations of dislocations control their mobility and set the time-scale of thermally activated events such as cross-slip or obstacles by-pass. While dislocation vibrations have been previously investigated using simplified line tension descriptions and numerical dislocation dynamics models, we analyze them by the means of an analytical approach combined with atomistic simulations. Within the framework of the non-singular dislocation theory, we derived an analytical expression for the elastic energy of a weakly perturbed dislocation, which controls the amplitude of the equilibrium thermal fluctuations through the equi-partition theorem. Comparing this analytical prediction with molecular dynamics calculations performed in aluminum shows that a core energy (proportional to the dislocation length) has to be incorporated in addition to long-range elasticity. Adding this contribution allows to reproduce very accurately the fluctuation spectra obtained from molecular dynamics simulations and yields quantitative estimates for the core parameter of the non-singular theory and for the magnitude of the core energy. We also discuss the transferability of these parameters to the bowing-out of a dislocation between obstacles. Finally, a deeper analysis of the time-dependence of the fluctuations yields valuable insights on the dynamical behavior of dislocations, namely their mass and phonon damping.