Diffusion in dilute Mg with various impurities was investigated using first-principles density functional theory in the local density approximation. Impurity diffusion coefficients were computed as a function of temperature using the 8-frequency model which provided the relevant impurity and solvent (Mg) jump frequencies and correlation factors. Minimum energy pathways for impurity diffusion and associated saddle point structures were computed with the climbing image nudged elastic band method. Vibrational properties were obtained with the supercell (direct) method for lattice dynamics. Calculated diffusion coefficients were compared with available experimental data. For diffusion between basal planes, it was found that DMg–Ca > DMg–Zn > DMg–Sn > DMg–Al, where D was the diffusion coefficient. For diffusion within a basal plane, the same trend held, except that DMg–Zn overlaps with DMg–Al at high temperatures and DMg–Sn at low temperatures. These trends were explored with charge density contours in selected planes of each Mg–X alloy, the variation of the activation energy for diffusion with the atomic radius of each impurity and the electronic density of states. The theoretical methodology developed herein could be applied to impurity diffusion in other hexagonal materials.

First-Principles Calculations of Impurity Diffusion Coefficients in Dilute Mg Alloys using the 8-Frequency Model. S.Ganeshan, L.G.Hector, Z.K.Liu: Acta Materialia, 2011, 59[8], 3214-28