Medium-range order in liquid Al5Fe2 alloy

The molecular-dynamics (MD) simulation on liquid Al5Fe2 is carried out to investigate the structure of medium-range order (MRO), combined with X-ray diffraction experiment. The pre-peak considered as the signature of MRO is observed in the experiment, which is in good agreement with our simulation. According to the structure feature of atomic clusters, we find that there exist many icosahedral clusters in the liquid, which results in the pre-peak of S(Q). It is found from the calculated Ashcroft-Langreth (A-L) structure factors that there exists strong interaction force between Al and Fe atom. Both the Bhatia-Thornton (B-T) structure factors and the chemical short-range order parameter α indicate the preference for unlike-neighbor bonds. It is seen from the low-Q region of S(Q) and the concentration-concentration structure factor SCC(Q) that the pre-peak mainly comes from the first peak of SCC(Q). In other words, the pre-peak originates from the chemical ordering in the liquid