Platelike structures of semiconductor clusters Gen (n=40–44)

A remarkable mixture of germanium with phosphorus and arsenic atoms making stable pentagonal hetero-prisms [M@Ge5E5]+, E = P, As and M = Fe, Ru, Os

A pentagonal hetero-prismatic structural motif was found for singly transition metal doped M@Ge₅E₅⁺ clusters, where the transition metal atom is located at the centre of a (5/5) Ge₅E₅ prism in which Ge is mixed with either P or As atoms. Structural characterization indicates that each (5/5) Ge₅E₅ prism is established by joining of two Ge₃E₂ and Ge₂E₃ strings in a prismatic fashion rather than two Ge₅ and E₅ strings. Each string results from a remarkable mixture of Ge and E atoms and contains only one E–E connection due to the fact that Ge–E bonds are much stronger than E–E connections. From the donor–acceptor perspective, the Ge₅E₅ tube donates electrons to the M center, which behaves as an acceptor. NBO atomic charge and ELI_D analyses demonstrate such electrostatic interactions of the M dopant with a Ge₅E₅⁺ tube which likely induce thermodynamic stability for the resulting M@Ge₅E₅⁺ cluster. CMO analysis illustrates that the conventional 18 electron count is recovered in the M@Ge₅E₅⁺ cations.

Geometric shape of the lowest-energy structure M@Ge₅E₅⁺.

Transformation between Hexagonal Prism and Antiprism of the Singly and Doubly Cr-Doped Ge12 Clusters

Structural transformation is a unique characteristic of atomic clusters, but it turns out very different from cluster to cluster. This theoretical study proves that the isomeric transformation between hexagonal prism and hexagonal antiprism is found for the doubly doped Cr₂Ge₁₂ cluster but not for singly doped CrGe₁₂ cluster. We confirm that the ground state of CrGe₁₂ is the distorted hexagonal prism C_2h at the ³B_g triplet state instead of various shapes predicted in the previous studies. Upon comparison between the estimation at the B3P86/6-311+G(d) level of theory and the detachment energies measured by photoelectron spectroscopy, hexagonal antiprismatic shape is identified as the most stable isomer of the Cr₂Ge₁₂ cluster and it is easy to transform to the hexagonal prism-a less stable isomer by the rotation of the hexagonal rings. That is the first evidence for the structural transformation between a hexagonal prism and an antiprism of the germanium clusters, referring to the ability of Ge-based clusters in the formation of tubular geometry by doping Cr atoms. All the low-energy isomers of both Cr-doped germanium clusters have high magnetic moments. Interestingly, there is a tuning in magnetic properties of Cr₂Ge₁₂ from the ferromagnetism of the lowest-lying hexagonal antiprism to the ferrimagnetism of the higher-energy hexagonal prism. The stronger Cr-Cr bond and stronger interaction between the Cr₂ moiety and the antiprism cage are accounted for by the higher stability of the hexagonal antiprismatic isomer.

Atomic scale dynamics of ultrasmall germanium clusters

Starting from the gas phase, small clusters can be produced and deposited with huge flexibility with regard to composition, materials choice and cluster size. Despite many advances in experimental characterization, a detailed morphology of such clusters is still lacking. Here we present an atomic scale observation as well as the dynamical behaviour of ultrasmall germanium clusters. Using quantitative scanning transmission electron microscopy in combination with ab initio calculations, we are able to characterize the transition between different equilibrium geometries of a germanium cluster consisting of less than 25 atoms. Seven-membered rings, trigonal prisms and some smaller subunits are identified as possible building blocks that stabilize the structure.

Structures of Pb(n) (n = 21-30) clusters from first-principles calculations

Neutral lead clusters Pb(n) (n = 21-30) were studied using a genetic algorithm (GA)/tight-binding (TB) search combined with density functional theory (DFT)-Perdew-Burke-Ernzerhof (PBE) calculations. The calculated results show that the Pb(n) (22 ≤ n ≤ 30) clusters favor endohedral cage structures with two (Pb(22 - 26)) or three (Pb(27 - 30)) endohedral atoms. The binding energies, stabilities, and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of the Pb(n) clusters were also discussed. The results from our calculations also indicate that Pb(24) and Pb(28) are especially stable clusters compared with their neighbors.