[PO-C1] Poster Session 1

[P1-12] Ab Initio Dislocation Core Calculations using a Cluster Model

^○Jonas Frafjord^1,3, Bjørn Holmedal⁴, Jesper Friisj^2,3, Randi Holmestad^1,3, Ingeborg-Helene Svenum², Inga Gudem Ringdalen² (1.Dept. of Physics, Norwegian University of Science and Technology, Norway, 2.SINTEF Industry, Trondheim, Norway, 3.Centre for Advanced Structural Analysis, SIMLab, Norway, 4.Dept. of Materials Science and Engineering, Norwegian University of Science and Technology, Norway)

Solute strengthening is an important mechanism contributing to the strength of metallic alloys. In order to create an accurate framework for strength calculations, this mechanism must be fully understood. In that regard, studies have shown that it is crucial to include the core region of a dislocation in models [1-3], as the core interacts strongly with solute atoms through short-range interactions, and affects the dislocation mobility. The core region can be treated from first principles to include electronic effects. One challenge has been to correctly describe the dissociation of a dislocation at atomic level [4,5]. Dissociation of a perfect dislocation results in a more favourable configuration by reduction of the elastic energy. The equilibrium separation of the partial dislocations generated is due to the cost of the intrinsic stacking fault. This separation width is important for the strengthening mechanism of solutes since it affects the solute-dislocation interaction-energy map.

In this work, a cluster model for dislocation core structures is applied. The model takes the shape of a cylinder, where the dislocation line is elongated through the centre [6]. It consists of an outer region surrounded by vacuum, where the atoms are fixed by an elastic displacement field, and a core region that is relaxed. This model is strongly dependent on the assumption that the elastic theory is respected within the fixed region. The advantage of this model is the simplicity, and its transparency towards the assumptions that are taken. The aim is to improve the capability to set up an atomistic model for dislocations in fcc metals using a cluster model with sufficient accuracy. The setup has been tested for Aluminium with a pure edge dislocation. It will be extended further to screw dislocations.

Using this simple model, the static configuration of a dislocation core structure can be compared to experimental observations and results using the flexible boundary condition applied by other groups [1,4].

[1] doi.org/10.1016/j.actamat.2016.09.046
[2] doi.org/10.1016/j.scriptamat.2014.04.018
[3] doi.org/10.1016/j.actamat.2010.06.045
[4] doi.org/10.1016/j.msea.2005.03.039
[5] 10.1103/PhysRevLett.100.045507
[6] doi.org/10.1016/j.actamat.2016.09.049