Atomistic calculations of dislocation core energy in aluminium

Abstract

A robust molecular dynamics simulation method for calculating dislocation core energies has been developed. This method has unique advantages: it does not require artificial boundary conditions, is applicable for mixed dislocations, and can yield converged results regardless of the atomistic system size. Utilizing a high-fidelity bond order potential, we have applied this method in aluminium to calculate the dislocation core energy as a function of the angle β between the dislocation line and Burgers vector. These calculations show that, for the face-centred-cubic aluminium explored, the dislocation core energy follows the same functional dependence on β as the dislocation elastic energy: E c = A·sin 2 β + B·cos 2 β, and this dependence is independent of temperature between 100 and 300 K. By further analysing the energetics of an extended dislocation core, we elucidate the relationship between the core energy and core radius of a perfect versus an extended dislocation. With our methodology, the dislocation core energy can be accurately accounted for in models of dislocation-mediated plasticity.

Uncertainty Quantification and Reduction of Molecular Dynamics Models

“…Here, we illustrate this by calculating core energies of edge type of misfit dislocation in zinc-blende CdS [20] using the literature interatomic potential [21]. We also calculated dislocation energies for aluminium using exactly the same geometry as shown in Figure 1(a), and the same results were obtained [22].…”

Generalized Kanzaki force field of extended defects in crystals with applications to the modeling of edge dislocations

“…Accordingly, the values of the core energy we find, although within the same order of magnitude as those commonly reported (see Refs. [77,78]), will nonetheless be different. For instance, we find that for fcc Al, over a few unit cells the V core converges to a value of about V core Al = −1.34 eV/Å.…”

“…(32) is notionally analogous to the classical definition of the core energy (see Refs. [27,44,77]). The line energy of a dislocation is divided into two superposed terms: an elastic term associated with the Volterra dislocation's energy and a core energy term that accounts for the differences between the total and elastic terms.…”

“…where r is the radial distance to the nominal dislocation line, and r 0 is the core radius; hereafter, the letter E is employed to distinguish the energy coming from continuum level considerations from the energy V coming from lattice level models. The core radius is defined as the radial distance above which the elastic fields of the dislocation satisfy linear elasticity [77]. This makes the core radius an ambiguously defined variable [78], with the value of the core energy heavily dependent on both its value and the assumption that the dislocation and its core are planar (cf.…”

Influence of defects on the thermal conductivity of compressed LiF

“…We considered two types of vacancies, a collocated (covacancy) and a separated Schottky Li-F pair vacancy, as well as a a/2 110 edge dislocation dipole. The energies are determined with long time (32 ns) averages at low temperature (≈1K) based on the work of Zhou et al 46 which showed that this approach leads to estimates that are superior to energy minimization techniques.…”