Magnetic and electronic properties of rhodium clusters

We have used all-electron local (LDA) and nonlocal (GGA) approximations to the density-functional theory to determine binding energies, equilibrium geometries, vibrational frequencies, and magnetic properties of Rh_N clusters (N<~6). We present careful tests on the Rh₂ dimer that compare results as calculated with a large (18-single Gaussian) and a very large (23-single Gaussian) basis sets. While the smaller set of Gaussians leads to underconverged results, we find that the large basis set leads to converged results that are also in excellent agreement with the experimental data available for Rh₂. The ground state of Rh₂ is confirmed to be a quintuplet, the trigonal Rh₃ is predicted to be a sextuplet, Rh₄ in its tetrahedral configuration is a singlet, Rh₅ sextuplet is a square pyramid, and Rh₆ septuplet is the octahedron. Results from several excited states are calculated and presented as well. It is found that LDA overestimates the binding energy but that GGA corrects this deficiency and predicts longer bond lengths.