Geometries and electronic properties of Ta_n, Ta_nO and TaO_n (n=1-3) clusters

Geometries, vibrational frequencies, electron affinities, ionization potentials and dissociation energies of the title clusters in both neutral and positively and negatively charged states were studied by use of density functional theory. For both neutral and charged species, different initial isomers were studied in order to determine the structure with the lowest energy. Vibrational analysis was also performed in order to characterize these isomers. For Ta₂, Ta-Ta metallic bond is strengthened by adding or removing an electron, i.e. the charged species are much more stable than the neutral counterpart. For Ta₃, equilateral triangle with D_3h symmetry has the lowest energy for both neutral and charged species (near equilateral triangle for cation). TaO and its charged species have much larger dissociation energy compared with other tantalum oxides. For Ta₂O and TaO₂, structure with C_2v symmetry is much more stable than linear chains. For Ta₃O, planar structure with doubly bridging oxygen atoms of C_2v symmetry is the global minimum for both neutral and charged species. While for TaO₃, three-dimensional structures are favored for both neutral (C₁ symmetry) and charged species (C_3v symmetry). The calculated results were compared with available experimental and previous theoretical studies.