Ab initio computational study of Ga in an Al grain boundary

Gallium as an impurity in aluminium is an extreme example of a grain boundary embrittler. The energetics of substituting Ga in various sites, individually and together, has been calculated by ab initio techniques in a Sigma = 11 (1 1 3) symmetric tilt boundary. This boundary has one relatively short nearest-neighbour distance across the boundary, which is relaxed on substitution by Ga. A picture is developed of the attraction of Ga towards the tight sites in the Al grain boundaries, and of its role as a substitutional embrittling impurity.