Density functional study of geometrical, electronic and magnetic properties of Wn clusters (n = 2–16, 19, 23)

Abstract

Geometrical, electronic and magnetic properties of Wn atomic clusters, with n = 1–16, 19, 23, are explored using different generalized gradient approximations to the density functional theory and basis sets of double-ζ quality augmented with polarization functions. From a geometrical point of view, tungsten aggregates with n = 15 and above exhibit a clear tendency to adopt structures derived from the body-centered cubic system. Total energy second-differences indicate that tungsten octamer becomes a specially stable isomer. For larger sizes, the different generalized gradient approximations do not predict the same stability pattern. Vertical ionization energies show a smooth, but slow trend to the experimental work function of polycrystalline tungsten. Vertical electron affinities agree very well with experimental measures of detachment electron energies. Calculated magnetic moments indicate that mainly singlet, triplet and quintet electronic states characterize small tungsten aggregates. A W15 isomer with a geometry derived from the body-centered cubic system, however, is characterized by an electronic state with 14 unpaired electrons.