Molecular dynamics study of atomic-level structure in monatomic metallic glass

• The growth of icosahedral clusters is composed of the intercross-sharing linkage.
• Distorted icosahedral clusters are more dominant than the full icosahedral clusters.
• Splitting of the 2nd peak in RDF is caused by the distorted icosahedral clusters.

Molecular dynamics simulations have been performed to study the vitrification process and the local atomic structures in Ni monatomic metallic glasses (MG). The interatomic interactions are described by embedded atom method (EAM) potentials. Short-range order (SRO) and medium range order (MRO) in nickel monatomic MG is studied using several structural techniques such as the Radial distribution function (RDF); the Common neighbor analysis method (CNA) and the Voronoi tessellation. As a result, we found that the atomic packing in metallic glasses can be described globally as a superposition of the spherical-periodic order (SPO) and the local translational symmetry (LTS). From CNA method, we found that the majority of icosahedral clusters in Ni monatomic MG are connected together by vertex-sharing (VS), edge-sharing (ES), face-sharing (FS) and intercross-sharing (IS) rather than isolated clusters. These typical cluster connections constitute to the partial RDF of icosahedral atoms except the edge sharing which is hidden between the second and the third subpeaks of RDF. Furthermore, the visualization technologies are applied to follow the formation of clusters during rapid quenching. It is found that the clusters ⟨0,1,10,2⟩ and ⟨0,2,8,4⟩ are more dominant than the full icosahedral polyhedron ⟨0,0,12,0⟩ in our monatomic system. Furthermore, the splitting of the second peak in RDF curve in Ni glass is not only caused by the icosahedral clusters, but also by the Voronoi polyhedrons ⟨0,1,10,2⟩ and ⟨0,2,8,4⟩.