The first-principles prediction of dislocation nucleation in metallic systems subject to realistically sized indenters required a multi-scale approach due to the prohibitive computational expense. The largest empirical atomistic simulations included at most a billion atoms, at the same time requiring the parameterization of new interactions whenever an additional species or crystal structure was added. The multi-scale orbital-free density functional theory-local quasi-continuum method overcame these problems by using first-principles orbital-free density functional theory to capture the atomic interactions while relying upon local quasi-continuum to evolve the macroscopic system. This method was used to indent the (111) surface of a 2 x 2 x 1μm piece of L12 Al3Mg. Using a localization criterion, the first dislocation was predicted to form off-axis on the (1¯1¯1) slip plane in the [01¯1] direction after the indenter had penetrated 70nm. Other popular dislocation nucleation criteria led to different predictions. The results were very similar to those found for the indentation of (111)Al. This indicated that the underlying crystal structure, and not the atomic identity, was the most important factor determining the onset of plasticity.

Prediction of Dislocation Nucleation during Nano-Indentation of Al3Mg by the Orbital-Free Density Functional Theory Local Quasi-Continuum Method. R.L.Hayes, G.Ho, M.Ortiz, E.A.Carter: Philosophical Magazine, 2006, 86[16], 2343-58