Molecular dynamics calculations of the crystal-melt interfacial mobility for hexagonal close-packed Mg

The kinetics of crystallization from the melt is investigated for hcp Mg employing molecular dynamics simulations based on a recently developed embedded-atom-method interatomic potential. The interface mobility $\left(\mu \right)$, defined as the constant of proportionality between interface velocity and undercooling, is calculated for the three high-symmetry orientations (0001), $\left(10\overline{1}0\right)$, and $\left(11\overline{2}0\right)$. The magnitudes of the interface mobilities are found to lie in the range of $40–80\mathrm{cm}∕\mathrm{s}∕\mathrm{K}$. The mobilities ${\mu }_{10\overline{1}0}$ and ${\mu }_{11\overline{2}0}$ are found to be of comparable magnitude and approximately 1.7 times larger than ${\mu }_{0001}$. The calculated dependence of $\mu$ on interface normal is discussed within the framework of the kinetic density-functional theory (DFT) formulation of Mikheev and Chernov.

Figure 1

The volume as a function of time during a free solidification simulation for a $\left(10\overline{1}0\right)$ oriented interface with 12 000 particles. The thin lines represent results from three independent runs, while the thick line is the average.

Figure 2

Velocity of the crystal-melt interface vs temperature for Mg in the (0001), $\left(10\overline{1}0\right)$, and $\left(11\overline{2}0\right)$ directions. The solid lines are linear-least-squares fits to the data, the slopes of which yield the value of the interface mobility.