Ab initiosimulations of geometrical frustration in supercooled liquid Fe and Fe-based metallic glass

Abstract

We investigate short range order in liquid and supercooled liquid Fe and Fe-based metallic glass using ab initio simulation methods. We analyze the data to quantify the degree of local icosahedral and polytetrahedral order and to understand the role of alloying in controlling the degree of geometric frustration. Comparing elemental Fe to Cu [P. Ganesh and M. Widom, Phys. Rev. B 74, 134205 (2006)] we find that the degree of icosahedral order is greater in Fe than in Cu, possibly because icosahedral disclination line defects are more easily incorporated into bcc environments than fcc. In Fe-based metallic glass-forming alloys ($\mathrm{FeB}$ and $\mathrm{FeZrB}$) we find that introducing small concentrations of small B atoms and large Zr atoms controls the frustration of local icosahedral order.