Effect Of Magnetism On The Geometry Of Transition-metal Monometallic And Bimetallic Nanoparticles From First Principles

Transition metal clusters and the derived bimetallic nanoparticles have attained much attention in material science. In particular, bimetallic clusters exhibit unique structural and magnetic properties and can be used to design new materials and catalysts with high catalytic activity. In this work, density functional theory (DFT) calculations have been used to investigate the geometry, magnetism and segregation preference of transition metal clusters of twelve elements. The main points are as follows:1. Clusters of certain numbers (magic number) of atoms are energetically more favorable. The calculations of monometallic clusters of13,55, and147atoms show that cuboctahedron, truncated decahedron, and icosahedron are stable configurations. With increasing the number of atoms involved in clusters, icosahedron becomes more stable.2. The magnetic calculations of the clusters of13,55, and147atoms indicate that not only the3d-block magnetic metals but also the nonmagnetic metals show great magnetic moments.3. The calculations of segregation energies for the late transition-metal binary-alloy clusters at various sizes indicate that the segregation preference is similar. The segregation site preference for the clusters of147atoms is also reported.4. The nonspin-polarized and spin-polarized calculations indicate that magnetism has a significant effect on the segregation preference, and its contribution is weakened with increasing the number of atoms involved in clusters. Metal atoms with greater magnetic moments tend to be enriched in the cores of clusters, while metals with lower magnetic moments will occupy the shells of clusters.