材料期刊网

The electronic properties and magnetism of Ru-N clusters (N = 4, 6, 10, 13, 19, 43, and 55) are studied using the discrete-variational local-spin-density-functional method. The bond lengths in the clusters with N less than or equal to 13 are optimized, and the cluster binding energies are found to increase monotonically with the increase of cluster size. All clusters except Ru-19 are shown to have magnetic ground states. The average magnetic moments per atom for the Ru-N are found to decrease rapidly with the increase of the cluster size, although small oscillation exists. The calculated moments per atom for Ru-10 and Ru-13 clusters are in good agreement with the experimental values. Multiple magnetic solutions are explored, and double magnetic solutions an found for the icosahedral (I-h) Ru-13 cluster which is used successfully to eliminate the contradiction between the previous theory and experiment on the moment of Ru-13 cluster. The electronic structures of Ru-N clusters are calculated, and indicate that all clusters are metallic in behavior. The comparison between the Ru-55 cluster and the bulk counterpart indicates that Ru-55 has shown bulklike properties in the binding energy, magnetism, valence-bandwidth, and density of states. Based on electronic-structure results, the reactivity of Ru-6, Ru-19, and Ru-43 clusters toward H-2, N-2, and CO molecules is predicted.