Theoretical prediction for growth behavior and electronic properties of monoanionic Ru2Gen- (n=3-20) clusters

We present a detailed theoretical study on the structural and electronic properties of monoanionic Ru2Gen- (n = 3-20) clusters using comprehensive genetic algorithm combined with density functional theory (CGA-DFT). It is shown that the geometrical growth patterns of the ground state Ru2Gen- clusters are polyhedral pyramidal structures with n <= 9 and gradually to form pentagonal prism-based structures with two endohedral Ru atoms from 10 <= n <= 15, then the structures evolve into a oblate cage-like configuration with two Ru atoms in center from cluster sizes n >= 16. In general, one extra electron will influence the geometric structures of Ru2Gen clusters to compare with their neutral ones we have studied. Based on the obtained ground state structures, we find that the clusters of Ru2Ge10-, Ru2Ge12- and Ru2Ge14- have relatively higher structural and chemical stability in which Ru2Ge14- is more prominent through the analysis of binding energy, second order of energy difference and highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap. Furthermore, we analyzed natural charge, natural electronic configuration, the frontier molecular orbitals and orbital composition to verify the clusters of Ru2Gen- with n = 10, 12, 14 and 16 have relatively higher chemical stability owning to the less contribution of Ru-d orbitals. In addition, the clusters of Ru2Ge3-, Ru2Ge4-, Ru2Ge4-, Ru2Ge6- and Ru2Ge10- and Ru2Ge16- have magnetic moment of 3 mu(B), while others are 1 mu(B). And also the vertical detachment energy (VDE) and adiabatic detachment energy (ADE) for all ground state clusters are computed to support future experiment.

Automated summary

In this study, a comprehensive genetic algorithm combined with density functional theory (CGA-DFT) was used to investigate the structural and electronic properties of monoanionic Ru2Gen- (n = 3-20) clusters. The results reveal that the geometric growth patterns of the ground state Ru2Gen- clusters vary with cluster size, and the presence of an extra electron affects the geometric structures. Based on the obtained ground state structures, it is found that Ru2Ge10-, Ru2Ge12-, and Ru2Ge14- clusters exhibit relatively higher structural and chemical stability, with Ru2Ge14- showing the most prominent stability.