AB-INITIO COMPUTATIONAL STUDY OF GA IN AN AL GRAIN-BOUNDARY

Gallium as an impurity in aluminium is an extreme example of a grain b oundary embrittler. The energetics of substituting Ga in various sites , individually and together, has been calculated by ab initio techniqu es in a Sigma = 11 (113) symmetric tilt boundary. This boundary has on e relatively short nearest-neighbour distance across the boundary, whi ch is relaxed on substitution by Ga. A picture is developed of the att raction of Ga towards the tight sites in the Al grain boundaries, and of its role as a substitutional embrittling impurity.