Abstract: The microstructure of liquid Al80Fe20 alloy is studied by molecular dynamics simulation, combined with experiment of Xray diffraction. It is found that there exists an obvious prepeak in the small domain（Q=17.5 nm－1）of the structure factor, which is considered as indicative of the existence of mediumrange order(MRO) in the liquid. Furthermore, the results of MD simulation agree also well with those of experiment. The chemical shortrange order(CSRO) α and BhatisThornton(BT) partial structure factors show that there exists very strong CSRO in the liquid, which suggests that the CSRO result in the formation of MRO. The maximum and the minimum at Q=17.5 nm－1 in SFe－Fe(Q) and SAl－Fe(Q) of FaberZiman(FZ) partial structure factors also indicate the existence of superstructure in the liquid. We also calculate the coordination numbers of the system and give a structural model representing MRO clusters.

Key words: Al₈₀Fe₂₀ liquid alloy, Mediumrange order, MD simulation, Structure factor, Prepeak