Structure and magnetism of rhodium particles as a size effect

The magnetic properties of Rh clusters with face-centered-cubic (FCC) and hexagonal-closed-packed (HCP) structures were studied by first-principles calculations. The results show that both the structure and magnetic properties have size effects. Bulk Rh exists as a FCC structure. However, as the size of Rh particles shrinks, the FCC and HCP structures have comparable energies, consistent with the coexistence of the two structures experimentally observed previously. Although the bulk Rh is nonmagnetic, the nanoparticles or clusters of Rh in both the FCC and HCP structures are magnetic. The average magnetic moment gradually increases as the clusters shrink. The origin of the magnetism of Rh clusters can be attributed to the reduction of coordination number, other than the lattice expansion. The findings provide insights for understanding the magnetic properties of noble metal clusters.