Size and composition dependence of the frozen structures in Co-based bimetallic clusters

► The size effect occurs in the Co, Co-Ni, and Co-Cu clusters. ► The clusters with large sizes always freeze to form their bulk-like structures. ► The frozen structures for small sizes are generally related to their compositions. ► Icosahedron is formed for Co and also for Co-Ni but at a larger size range. ► Upon the Co-Cu clusters, decahedral structure is obtained for small size.