[SY-E2] First principles studies of H interaction with the face-centred cubic Al Σ5 [100] twist grain boundary during a uniaxial tensile test
For the theoretical examination of intergranular fracture, ab initio investigations of grain boundaries (GBs) subjected to loading play a central role. While the modelling of material failure is an inherently multi-scale task, a first principles framework often provides unmatched accuracy for the description of atomic rearrangements and bond breakage at the heart of the region of key interest. At the same time, it is integral to a meaningful analysis that the atomistic traction-separation curve emerging from density functional theory (DFT) based studies be coupled self-consistently to the stress field of the surrounding bulk grain. The absence of a robust solution to this challenge has manifested itself as a “cell size convergence problem” for the computed atomistic GB properties. In this talk, we first show how this obstacle may be entirely circumvented for the modelling of metal GBs within a standard DFT framework. (F. J. H. Ehlers et al., Comput. Mater. Sci. 139, 39 (2017)) In the procedure, we delimit a GB “local region” outside which the system response to deformation bears no significant evidence of the presence of a nearby GB. Then, we show through the example of H decoration of the fcc Al Σ5 36.87° [100] twist GB how this platform may be used efficiently for quantifying the influence of impurities on a metal GB in a multi-scale modelling scenario. The H formation energies at the various unequivalent sites in the vicinity of the GB evolve differently with the increase of tensile strain. Finally, the H impact on the full TSL curve assuming fast diffusion of H atoms at the most stable sites during elongation is assessed.