Structural evolution and dynamical properties of Al2Ag and Al2Cu liquids studied by experiments and ab initio molecular dynamics simulations

Abstract The structural evolution and dynamical properties of Al 2 Ag and Al 2 Cu liquids have been investigated in the temperature range of 943–1153 K by synchrotron X-ray diffraction and ab initio molecular dynamics simulations. It is demonstrated that the local atomic packing of Al 2 Ag liquid has lower ordering than the Al 2 Cu liquid, in which Al and Ag atoms are more randomly distributed while Al and Cu atoms tend to form pairs. With decreasing temperature, the bond-angle distributions of Ag Ag Ag and Ag Al Ag triplets shift to 60°, indicating that the local ordering transforms from the icosahedron-like to the hexagonal close-packed structure, while the Cu Cu Cu and Cu Al Cu triplets have the similar angles to those in the crystalline Al 2 Cu compound. These are consistent with the major Voronoi polyhedrons in both liquids. The dynamic results reveal that Al and Ag atoms diffuse much easier in the Al 2 Ag liquid than Al and Cu in the Al 2 Cu liquid, making Al and Ag atoms more randomly distributed and thus reducing the local ordering in the Al 2 Ag liquid.