Structural, electronic, and vibrational properties of neutral and charged [Formula Presented] clusters

We present a theoretical study of the structural, vibrational, and electronic properties of small niobium clusters [Formula Presented] [Formula Presented] and [Formula Presented] using density-functional theory with local as well as gradient-corrected exchange correlation density functionals. For [Formula Presented] and [Formula Presented] several low-energy structures were obtained, whereas for [Formula Presented] there seems to be only one isomer that is energetically preferred. Vibrational spectra are in the range 100–300 [Formula Presented] and are sensitive to the structure. Electronic properties are investigated by means of the densities of states, which depend strongly on the geometry. The theoretical results for the ionization potentials and vertical detachment energies are in good agreement with available experimental data. © 1998 The American Physical Society.