Atomistic underpinnings for orientation selection in alloy dendritic growth

C. A. Becker and D. Olmsted and M. Asta and J. J. Hoyt and S. M. Foiles, Phys Rev Lett, 98, 125701 (2007).

In dendritic solidification, growth morphologies often display a pronounced sensitivity to small changes in composition. To gain insight into the origins of this phenomenon, we undertake an atomistic calculation of the magnitude and anisotropy of the crystal-melt interfacial free energy in a model alloy system featuring no atomic size mismatch and relatively ideal solution thermodynamics. By comparing the results of these calculations with predictions from recent phase-field calculations, we demonstrate that alloying gives rise to changes in free-energy anisotropies that are substantial on the scale required to induce changes in growth orientations.

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