Structural and electronic properties of small titanium clusters: A density functional theory and anion photoelectron spectroscopy study

Density functional theory calculations using the generalized-gradient approximation have been carried out on the structural and electronic properties of Ti-n(-) and Ti-n clusters for n=3-8 and 13. Many low-lying states, of different spins and geometries, were found for each Ti-n(-) and Ti-n species. We observed that the calculated density of states (DOS) and the adiabatic electron binding energies for the ground state of a given anion are in good agreement with experimental photoelectron spectroscopy (PES) data, lending credence to the assignments of the ground state structures. Comparison between the calculated DOS and the PES data for other low-lying states made it possible to affirm contributions of these states to the spectra, allowing the characterization of the ensemble or composition of a given Ti-n(-) system. We found that all the clusters possess highly compact structures, and Ti-7 and Ti-13 have distorted pentagonal bipyramidal and icosahedral structures, respectively. From the ground state spin states, insight into the magnetic properties of the clusters and their evolution with size was also obtained. Small Ti clusters with n<5 are highly magnetic, but the magnetic moment drops rapidly with size. (C) 2003 American Institute of Physics.