[SY-C8] Tension of fluctuating dislocation lines
Fusion materials will be subjected to high lifetime doses of irradiation at high temperatures. To accurately predict changes in mechanical properties of materials under fusion conditions, we need to simulate complex stochastically-driven evolution of radiation damage defect networks over a broad range of temperature and timescales.
Recent analysis shows that fundamental concepts underpinning defect dynamics require re-examination. In stark disagreement with atomistic simulations, linear elasticity theory predicts that straight dislocations have negative line tension with respect to small fluctuations, suggesting that dislocations are unstable to bow-out. Consequently, a dislocation dynamics model based solely on linear elasticity is unable to cope with stochastic thermal fluctuations.
A consistent treatment of dislocation cores is a prerequisite for correctly describing dislocation line tension in a continuum model. We present a new solution of the discrete Multi-String Frenkel-Kontorova (MSFK) model, which in the continuum limit unifies linear elasticity and the Peierls-Nabarro model for an edge dislocation. The core (misfit) energy and core width are controlled by a single parameter. We find the continuum displacement fields in agreement with atomistic displacements derived from molecular dynamics simulations of edge dislocations in bcc iron and tungsten. We investigate line tension of the continuum MSFK model with respect to bow-out and find that the misfit energy plays a crucial role in controlling the stochastic line instabilities.
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. Also, it has been part-funded by the RCUK Energy Programme (Grant Number EP/P012450/1). The views and opinions expressed herein do not necessarily reflect those of the European Commission.
Recent analysis shows that fundamental concepts underpinning defect dynamics require re-examination. In stark disagreement with atomistic simulations, linear elasticity theory predicts that straight dislocations have negative line tension with respect to small fluctuations, suggesting that dislocations are unstable to bow-out. Consequently, a dislocation dynamics model based solely on linear elasticity is unable to cope with stochastic thermal fluctuations.
A consistent treatment of dislocation cores is a prerequisite for correctly describing dislocation line tension in a continuum model. We present a new solution of the discrete Multi-String Frenkel-Kontorova (MSFK) model, which in the continuum limit unifies linear elasticity and the Peierls-Nabarro model for an edge dislocation. The core (misfit) energy and core width are controlled by a single parameter. We find the continuum displacement fields in agreement with atomistic displacements derived from molecular dynamics simulations of edge dislocations in bcc iron and tungsten. We investigate line tension of the continuum MSFK model with respect to bow-out and find that the misfit energy plays a crucial role in controlling the stochastic line instabilities.
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. Also, it has been part-funded by the RCUK Energy Programme (Grant Number EP/P012450/1). The views and opinions expressed herein do not necessarily reflect those of the European Commission.