Local cluster formation in a cobalt melt during the cooling process

Investigations of the thermal evolution of the structural and dynamic properties of small cobalt clusters in melt are performed using molecular-dynamics simulations with a Finnis-Sinsclaire potential. The mean square displacements, atomic volume, and internal energy, as well as the pair correlation function and bonded pairs, are obtained from quick and slow cooling simulations, respectively. The splitting of a second peak of pair correlation function is due to the presence of icosahedron-type clusters. The results demonstrate that the transition from a supercooled-liquid to a crystal is a discontinuous transition in structure, while the supercooled-liquid to glass transition is a continuous transition in structure. The physical picture of the structure of metallic glass is a disordered entanglement with a lot of icosahedra.