Structural evolution and magnetic properties of anionic clusters Cr₂Ge_n (n = 3-14) : Photoelectron spectroscopy and density functional theory computation

The structural, electronic and magnetic properties of dual Cr atoms doped germanium anionic clusters, Cr2Ge.n (n = 3.14), have been investigated by using photoelectron spectroscopy in combination with density-functional theory calculations. The low-lying structures of Cr2Ge.n are determined by DFT based genetic algorithm optimization. For Cr2Ge.n with n . 8, the structures are bipyramid-based geometries, while Cr2Ge.9 cluster has an opening cage-like structure, and the half-encapsulated structure is gradually covered by the additional Ge atoms to form closed-cage configuration with one Cr atom interior for n = 10 to 14. Meanwhile, the two Cr atoms in Cr2Ge.n clusters tend to form a Cr.Cr bond rather than be separated. Interestingly, the magnetic moment of all the anionic clusters considered is 1 B. Almost all clusters exhibit antiferromagnetic Cr.Cr coupling, except for two clusters, Cr2Ge.5 and Cr2Ge.6 . To our knowledge, the Cr2Ge.n cluster is the first kind of transition-metal doped semiconductor clusters that exhibit relatively stable antiferromagnetism within a wide size range. The experimental/theoretical results suggest high potential to modify the magnetic behavior of semiconductor clusters through introducing different transition-metal dopant atoms.