Effect of nanoclusters formed by metal impurity on magnesium vapor condensation in silicothermic process: a molecular dynamics study

Abstract

In the silicothermic process, some metal oxide impurities that coexist with dolomite are inevitably reduced to metal vapors, which condense to metal impurities in the magnesium crystallizer. In this paper, the molecular dynamics simulation method was adopted to investigate the effect of impurity clusters on the crystallization transition of undercooled magnesium vapor. The results showed that saturated vapor atoms tend to nucleate on the pre-existing impurity cluster, promoting the crystallization rate of magnesium vapor. The promoting effects of impurity clusters on the crystallization of magnesium vapor depend on their sizes and species. The cluster with a larger size demonstrated a more substantial promoting impact. Moreover, in the three impurities studied in this paper, magnesium vapor condenses on the Fe cluster at the fastest rate due to the bcc structure of the Fe cluster and the strong interaction between Fe and Mg atoms. For Ni and Cu clusters with the same fcc structure, the promoting effect of the Ni cluster on the crystallization of Mg vapor is more evident because the interaction between Ni-Mg atoms is stronger than between Cu-Mg atoms.