Basal slip in Laves phases: The synchroshear dislocation

Abstract

Two different mechanisms have been reported in previous ab initio studies to describe basal slip in complex intermetallic Laves phases: synchroshear and undulating slip. To date, no clear answer has been given on which is the energetically favourable mechanism and whether either of them could effectively propagate as a dislocation. Using classical atomistic simulations supported by ab initio calculations, the present work removes the ambiguity and shows that the two mechanisms are, in fact, identical. Furthermore, we establish synchroshear as the mechanism for propagating dislocations within the basal plane in Laves phases.

Laves phase crystal analysis (LaCA): Atomistic identification of lattice defects in C14 and C15 topologically close-packed phases

“…The synchro-Shockley dislocations were obtained from our previous study on the synchroshear mechanism using nudged-elastic band (NEB), where details of the simulations can be found [28].…”

“…In Laves phases, plastic deformation occurs via dislocationmediated processes. Dislocation motion on the basal plane in the hexagonal and the {111} plane in the cubic Laves phases occurs by synchroshear, characterized by two synchro-Shockley dislocations moving on adjacent planes of the triple layer [16,20,28]. Figure 3c shows the core structures of two typical synchro-Shockley dislocations with mixed characters (60° and 30°) in C14 Mg 2 Ca.…”

Assessment and optimization of the fast inertial relaxation engine (fire) for energy minimization in atomistic simulations and its implementation in lammps

“…1(8)). neb simulations are performed with 18 intermediate configurations as described elsewhere [50]. The ff is the meam from Kim et al [49].…”

Defect phases – thermodynamics and impact on material properties

“…Or, more simply put, as the motion of a dislocation formed in the layer with the larger atomic species that forces the smaller atoms in the adjacent atomic layer to jump out of its way sideways. The associated stacking faults were first imaged at high resolution in 2005 [158], but it was not until 2019 that, after several studies using DFT calculations only [159,160], the motion of a synchroshear dislocation was confirmed in atomistic simulations [156].…”