Towards an understanding of liquid-metal embrittlement: Energetics of Ga on Al surfaces

First-principles electronic structure calculations show that Ga wets the low Miller index surfaces of Al. Consistent with a thermodynamic basis for the observation that Ga causes single-crystal Al to crack along (100) planes, the Ga-covered (100) plane has the lowest surface energy. This represents a compromise between weaker Ga binding on closer-packed Al surfaces and higher clean surface surface energies on more open ones. In the second adsorbed Ga layer, on Al(100), several structures lie near the minimum total energy, consistent with rapid diffusion of Ga to a crack tip.