TOWARDS AN UNDERSTANDING OF LIQUID-METAL EMBRITTLEMENT - ENERGETICS OF GA ON AL SURFACES

First-principles electronic structure calculations show that Ga wets t he low Miller index surfaces of Al. Consistent with a thermodynamic ba sis for the observation that Ga causes single-crystal Al to crack alon g (100) planes, the Ga-covered (100) plane has the lowest surface ener gy. This represents a compromise between weaker Ga binding on closer-p acked Al surfaces and higher clean surface surface energies on more op en ones. In the second adsorbed Ga layer, on Al(100), several structur es lie near the minimum total energy, consistent with rapid diffusion of Ga to a crack tip.