Kink-pair nucleation on dislocations under stress in the two-dimensional Frenkel-Kontorova model

摘要

We present static and dynamic simulations to study the thermally activated motion of dislocations. The model employed is the two-dimensional Frenkel-Kontorova model. The main interest is to allow simulations of dislocation dynamics over long-time periods (-600 ns), giving access to large ranges of applied stresses and temperatures. The kink-pair nucleation rates, determined from dynamical simulations, are studied as a function of the ratio between the kink-pair activation enthalpy and the thermal energy. The former is computed from static simulations based on the elastic nudged band method. We show here that the dislocation motion is composed of two regimes: a low-temperature regime where the nucleation rate follows a thermally activated exponential law and a high-temperature regime where the motion is slower than expected from the low-temperature exponential law. We evidence a correlation between successive dislocation jumps that stems from the dynamics of internal modes of the dislocation and impedes high-frequency nucleation events.