STRUCTURE FACTORS OF BINARY ALUMINUM-NICKEL AND TERNARY ALUMINUM-NICKEL-SILICON LIQUID ALLOYS

A calculation of the structure of binary Al-Ni and of ternary Al-Ni-Si alloys based on a multicomponent hard sphere model and a square well like interatomic potential is developed in connection with chemical sh ort range order in these alloys. Maret et al.(1) using the isotopic su bstitution method, measured the partial structure factors of the binar y Al80Ni20 alloy. They obtained a prepeak in the partial Ni-Ni structu re factor and a preminimum in the Ni-Al partial structure factor. We o btain the same features with a square well potential, but not with har d spheres. It has been shown by Chenal(2) that liquid ternary alloys a t an amorphisable composition such as Al65Ni15Si20 present a prepeak i n the total structure factor, which is absent al a slightly different compostion of Ni:Al75Ni5Si20. We show here that ternary hard sphere st ructure factors with additive hard spheres cannot explain any prepeak, while such a feature can be reproduced from square well attractions b ut only at the right composition.