Ostwald’s Step Rule in the Crystallization of Supercooled Magnesium from Molecular Dynamic Simulation

Using classical molecular dynamics simulation together with a modified many-body embedded atom model (MEAM) potential, we simulated the crystallization of supercooled liquid magnesium. Firstly, we analyzed the crystalline structure and some thermodynamic quantities to examine the validity of the potential for the crystallization of magnesium. Then, using averaged bond-orientational order (ABOO) parameters to characterize atoms, we found that the liquid atoms always transform firstly to the metastable body-centered cubic (BCC) atoms and then to the stable hexagonal close packed (HCP) atoms. This demonstrated the applicability of the Ostwald step rule to magnesium. Besides, we found the averaged bond-orientational order parameters Q ₆ of BCC atom was closer to liquid atom than HCP atom, which may explain the phenomenon of forming BCC firstly instead of HCP from liquid to some extent.