We employ a combination of ion mobility measurements and an unbiased systematic structure search with density functional theory methods to study structure and energetics of gas phase tin cluster cations, Sn-n(+), in the range of n = 3-15. For Sn-13(+) we also carry out trapped ion electron diffraction measurements to ascertain the results obtained by the other procedures. The structures for the smaller systems are most easily described by idealized point group symmetries, although they are all Jahn-Teller distorted: D-3h (trigonal bipyramid), D-4h (octahedron), D-5h (pentagonal bipyramid) for n = 5, 6, and 7. For the larger systems we find capped D-5h for Sn-8(+) and Sn-9(+), D-3h (tricapped trigonal prism) and D-4d (bicapped squared antiprism) plus adatoms for n = 10, 11, 14, and 15. A centered icosahedron with a peripheral atom removed is the dominant motif in Sn-12(+). For Sn-13(+) the calculations predict a family of virtually isoenergetic isomers, an icosahedron and slightly distorted icosahedra, which are about 0.25 eV below two C-1 structures. The experiments indicate the presence of two structures, one from the I-h family and a prolate C-1 isomer based on fused deltahedral moieties. (C) 2010 American Institute of Physics. [doi:10.1063/1.3514907]
