[Introduction] Magnetism in clusters of non-magnetic elements, Ru, Rh and Pd has attracted much attention. These elements lie in the periodic table just below the magnetic elements Fe, Co, and Ni whose clusters have been found to have enhanced magnetic moments as compared to bulk. It is expected that clusters of Ru, Rh, and Pd will develop magnetic moments. We focus and attention on ruthenium. Experiments show these clusters to be nearly non-magnetic, but theoretically these are not well understood.

[Method] The optimized structure calculations have been performed using the ab initio ultrasoft pseudopotential method. The generalized gradient approximation has been used for the exchange-correlation energy. A few selected structures have been optimized using the conjugate gradient method and in most cases, the low lying isomers were checked for other spin isomers.

[Result] We find that icosahedron is not of the lowest energy for Ru₁₃. The lowest energy structure has no atom at the center. It has the same trend as rhodium clusters, which we have already presented in the spring meeting. However, the magnetic moments are found to be much smaller on Ru clusters in agreement with experiments. We will make presentation for the properties of clusters with different number of atoms.