Structural and Electronic Properties of Ruthenium-Doped Germanium Clusters

We have performed a global minimum search for the multicharged ruthenium-doped germanium clusters with the formula RuGenq (n = 2-12, q = -2, -3) using a particle swarm optimization metaheuristic coupled with density functional theory computations. Leading candidates for the lowest energy forms have been identified. Among the global minimum geometries, going from the size of n = 2 to n = 12, it is perceived that the cluster growth is directed toward the formation of an endohedral aggregate. Particularly, the half encapsulated structures of RuGe7q and RuGe8q made the bridge between small open-shell (n = 2-6) geometries and the endohedral (n = 9-12) geometries. The endohedral constructions contain the Ru atoms at their interstitial positions. Particularly, the 10-vertex endohedral cluster RuGe102- has an unprecedented 3-connected C-3 nu polyhedral geometry. The positive values of highest occupied molecular orbital energies of global minimum anions depict the electronic instability. The countercation effect is discussed to show the compensation of Coulomb repulsion among excess negative charges. RuGe122- and RuGe123- have S4- and D2d- symmetric endohedral shapes, respectively, which match with the previous experimental results. The natural population analysis charge is also examined to understand the associated charge transfers.