Accelerated atomistic simulation of dislocations in nuclear materials

点击翻译按钮获取中文摘要

This research program aims to improve and use computer simulations to investigate crucial mechanical properties of metals and alloys used in Canadian nuclear power reactors. These simulations will focus on physical properties of the materials on the scale of a few atoms to a few million atoms. More specifically, the kinetics of dislocations will be modeled, with an unprecedented level of realism, both by modeling inter-atomic interactions accurately and by reaching timescales that are comparable with experimental timescales.Dislocations and their interactions with radiation-induced defects play a critical role in determining the properties of structural materials in nuclear power applications. They lead to deleterious effects such as radiation-induced hardening and embrittlement, as the materials are exposed to neutron radiation.These effects arise from processes that take place at the atomic (nano-) level and scale up to the macro-scale. Typical simulations efforts to model them have two major issues. First, the physical models to express interatomic interactions have limited predictive ability in the context of dislocation kinetics, especially in alloys. Second, the timescales accessible to conventional simulation methodsa few tens of nanosecondsare too short to simulate dislocation motion at realistic strain rates (typical simulations are 10 orders of magnitude faster than experiments).The objective of this research project is to address these two issues. The interatomic interactions issue will be addressed by developing an evolutionary algorithm, where not only are there adjustable parameters, but where the functional form is itself optimized. The issue related to timescales will be addressed by extending the kinetic Activation Relaxation Technique, a form of accelerated dynamics, to handle dislocations. This is a ambitious research plan, from a technical point of view. It requires state-of-the-art methods, such as evolutionary algorithms, machine learning and accelerated dynamics. This will require the graduate students involved in the project to master and improve these methods, which should in itself be of great interest for the atomistic simulations community. Furthermore, the ability to accurately model dislocation dynamics at the atomic level will have a profound impact not only for Canadian nuclear power applications, but also for the study of other metals and alloys, notably in the context of construction or transportation.