Ab initio molecular dynamics simulation on the glass forming ability of Ni-metalloid amorphous alloys

In this work, Ni80P14B6, Ni80B14C6 and Ni80P13C7 amorphous alloys are chosen to be studied by ab initio molecular dynamics simulation, so that the effects of the metalloid elements M (M:P, B and C) on the atomic structure and glass forming ability (GFA) of Ni-metalloid amorphous alloys can be investigated. The pair distribution functions (PDFs), Voronoi polyhedra (VPs) and bond-pair distributions (BPDs) analyses are used to investigate the atomic structure characteristics and the GFA of the three Ni-metalloid amorphous alloys. The PDF analysis indicates that the bonding of NiP and NiC is stronger than that of NiB, and further, PP, PB, PC and CC atomic pairs attract each other and exhibit the better solute-solute avoidance in Ni80P14B6 and Ni80P13C7 alloys, which is benefit to the GFA. On the contrast, the BB and BC atomic pairs tend to repel each other and exhibit the poor solute-solute avoidance in Ni80B14C6 alloy, which goes against the GFA. The analysis of the P-centered VPs shows that P atoms have two placeholder ways, which one is to locate in the center of the antiprism and the other is to locate at the substitute position of Ni atom. Furthermore, compared with Ni80P13C7 alloy, P atoms in liquid Ni80P14B6 alloy have more icosahedral-like P-centered clusters, which leads to a more complex structure of melts and thus is benefit to the GFA. The PDFs and VPs analyses suggest that the GFA of the three Ni-metalloid alloys is dropped in the order of Ni80P14B6, Ni80P13C7 and Ni80B14C6. The BPDs analysis indicates that the icosahedrons and tetrahedral clusters are the dominant short range order (SRO) in all the three Ni-metalloid alloys in the glass state (300 K).