Theoretical studies of the ground-state geometries, electronic structure, binding energies, ionization potentials, and magnetic moments of ${\mathrm{Rh}}_n$ $(n=2\mathrm{}–13)$ clusters have been carried out using a combination of molecular-dynamics and ab initio density-functional scheme including gradient corrections. For clusters containing less than eight atoms, the ground states have been determined by starting from several random configurations and minimizing the geometry using first-principles density-functional calculations. For larger clusters, the initial geometries were obtained via molecular-dynamics simulations based on a tight-binding many-body potential and reoptimized using the density-functional approach. The ground-state structures are all compact arrangements and the clusters containing 8, 9, 10, 11, and 12 atoms resemble icosahedral fragments. The clusters are shown to undergo progression of magnetic behaviors with size. While most clusters are ferromagnetic with varying magnetic moments, ${\mathrm{Rh}}_4$ and ${\mathrm{Rh}}_6$ are found to have nonmagnetic states that are nearly degenerate with ferromagnetic states. The variation in the magnetic moments is shown to be intimately linked to the electronic structure.

• Received 27 July 1998

DOI:https://doi.org/10.1103/PhysRevB.59.5214