Equilibrium geometries and electronic properties of transition metal clusters (Mn₅, Mn₆) have been investigated by means of the relativistic density functional approach. Present results show that these clusters exhibit rich structural varieties on the potential energy surfaces, while the spin polarization at each site and the corresponding magnetic moments are highly sensitive to structures. For Mn₅ cluster, the most stable structure is trigonal bipyramid with spin magnetism of 3 μ_B, and Mn₆ cluster has the most stable structure of ferromagnetic octahedron with spin magnetic moment of 16 μ_B. The more stable isomers of Mn₅ and Mn₆ correspond to different orientations of the atomic spins resulting from the interatomic exchange coupling.

Key words: transition metal cluster, metal bond, manganese