Atomic packing and fractal behavior of Al-Co metallic glasses

Abstract

The rapidly solidified Al-Co alloy is studied in a favored composition range of 25–75 at.% of aluminum (Al) by performing a set of classical molecular dynamics simulations (MD) based on the Embedded Atom Method (EAM). We have examined particularly the structure using several analyzing techniques such as: the radial distribution function (RDF), the Voronoi tessellation analysis and the structure factor. We observed a splitting in the second peak of both the RDF and the structure factor, indicating metallic glass formation. The Voronoi analysis shows that it is difficult to define a dominant type of coordination polyhedra for all compositions, manifesting two different Voronoi polyhedral (VP): <0,3,6,4> and <0,2,8,4>, and this distribution varies with increasing Al content. The structure factor is further examined via illustrating two of their important parameters: the full width at half maximum (FWHM) and the positon of the first sharp peak (FSP) as a function of the composition and the atomic volume, respectively. The first parameter showed a maximum for the Al50Co50 alloy according to the dominance of unlike pairs, while the second one revealed a power law that allowed to compute the fractal dimension which is almost comparable to that found out from the analysis of the cumulative coordination number (CN).