Theoretical insights of structural evolution and electronic properties of Ru2Gen (n=1-16) clusters

We present a study on dual ruthenium atom-doped germanium clusters, Ru2Gen (n = 1-16), using comprehensive genetic algorithm combined with density functional theory (DFT) calculation. The low-lying structures of Ru2Gen are re-optimized by DFT calculation implemented in Gaussian09 program. For small Ru2Gen with n <= 8, the ground state structures adopt exohedral structure with Ru dimer as core surrounding by Ge atoms, and Ge atoms tend to separate rather than aggregate to form polyhedral configurations. From cluster sizes n >= 9, half-encapsulated structures start to form, while the geometries of clusters with 12 <= n <= 15 are based on the regular pentagonal prism attached with extra Ge atoms. For Ru2Ge16, the geometry looks like a Ru dimer invaginated cage structure. Furthermore, we analyze their bonding characters, natural electron configurations, density of states and frontier molecular orbital. We predict that the clusters with number of Ge atom of n = 6, 8, 10, 13 have high structural and chemical stability. Interestingly, Ru2Ge3, Ru2Ge5, Ru2Ge7 and Ru2Ge9 clusters possess magnetic moment of 2 mu(B), which is different from the reported non-magnetism of monatomic doping. These results enrich the understanding of transition metal-doped Ge-n clusters.