Enhanced Icosahedral Order in Supercooled Liquid Iron

As part of a study of metallic glass-forming ability, we perform first-principles molecular dynamics simulations of supercooled liquid Iron. Analyzing the results according to the icosahedral order parameter $\hat {W}_6 $, we find that Iron exhibits enhanced icosahedral order compared with supercooled Copper and compared with dense random packing. Voronoi analysis confirms the enhanced order is in the form of 13-atom icosahedral clusters as well as characteristic Frank-Kasper type disclinated icosahedra. Upon further cooling the sample crystallizes to a BCC lattice, with the icosahedra clustering to form a novel point defect.