Geometries and energy separations of the electronic states of Ge5+ and Sn5+

We compute the geometries and energy separations of 13 low-lying electronic states of Ge-5(+) and Sn-5(+) with five different structures (edge-capped tetrahedron, C-2v; trigonal bipyramid, D-3h; tetragonal pyramid, C-4v; planar square, D-4h; and planar pentagon, D-5h). The complete active space multiconfiguration self-consistent-held method (CASSCF) followed by large scale multireference singles+doubles configuration interaction (MRSDCI) computations that included up to 3.77 million configurations are employed. It was found that upon ionization the symmetrical D-3h trigonal bipyramidal structures of Ge-5 and Sn-5 Jahn-Teller distort into nearly degenerate B-2(2) and (2)A(1) electronic states with edge-capped tetrahedral (C-2v) geometry. Atomization and dissociation energies of Ge-5(+) and Sn-5(+) as well as adiabatic ionization energies of Ge-5 and Sn-5 are computed. (C) 1998 American Institute of Physics.