Invited Lecture
Thermal fluctuations of dislocations

Thermal fluctuations of dislocations control their mobility and set the time-scale of thermally activated events such obstacles by-pass or kink-pair nucleation. While dislocation vibrations have been previously investigated using simplified line tension descriptions and numerical dislocation dynamics (DD) 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 over a large range of wave-vectors and yields quantitative estimates for the core parameter of the non-singular theory and for the magnitude of the core energy. We show that these parameters can be used in a higher scale DD model to reproduce accurately the dislocation behavior on short length-scales. Also, a deeper analysis of the time-dependence of the fluctuations yields valuable insights on the dynamical behavior of dislocations. Finally, we will discuss the transferability of our approach to high entropy alloys where a structural noise adds up to the thermal noise.