The quantum states in metal clusters are grouped into bunches of close-lying eigenvalues, termed electronic shells, similar to those of atoms. Filling of the electronic shells with paired electrons results in local minima in energy to give stable species called magic clusters. This led to the realization that selected clusters mimic chemical properties of elemental atoms on the periodic table and can be classified as superatoms. So far the work on superatoms has focused on non-magnetic species. Here we propose a framework for magnetic superatoms by invoking systems that have both localized and delocalized electronic states, in which localized electrons stabilize magnetic moments and filled nearly-free electron shells lead to stable species. An isolated VCs(8) and a ligated MnAu(24)(SH)(18) are shown to be such magnetic superatoms. The magnetic superatoms' assemblies could be ideal for molecular electronic devices, as the coupling could be altered by charging or weak fields.

The quantum states in metal clusters bunch into supershells with associated orbitals having shapes resembling those in atoms, giving rise to the concept that selected clusters could mimic the characteristics of atoms and be classified as superatoms. Unlike atoms, the superatom orbitals span over multiple atoms and the filling of orbitals does not usually exhibit Hund's rule seen in atoms. Here, we demonstrate the possibility of enhancing exchange splitting in superatom shells via a composite cluster of a central transition metal and surrounding nearly free electron metal atoms. The transition metal d states hybridize with superatom D states and result in enhanced splitting between the majority and minority sets where the moment and the splitting can be controlled by the nature of the central atom. We demonstrate these findings through studies on TMMg n clusters where TM is a 3d atom. The clusters exhibit Hund's filling, opening the pathway to superatoms with magnetic shells.magnetic superatoms | jellium model | superatomic shells T he quantum confinement of electrons in small compact symmetric metal clusters results in electronic shell sequence 1S, 1P, 1D, …, much in the same way as in atoms. This analogy, originally introduced through the electronic states in a "jellium sphere" where the electron gas is confined to a uniform positive background of the size of the cluster, extends beyond this oversimplified model (1-9). Numerous first principles electronic structure studies on metal clusters have demonstrated the close grouping of electronic states into shells and have further shown that the shapes of the cluster electronic orbitals resemble those in atoms. Experiments on the reactivity of clusters have provided evidence that clusters and atoms of similar valence shells exhibit analogous chemical patterns. For example, although bulk aluminum is readily oxidized by oxygen, an Al 13 − cluster with filled 1S 2 , 1P 6 , 1D 10 , 2S 2 , 1F 14 , and 2P 6 shells exhibits strong resistance to etching by oxygen typical of inert atoms (5, 10). Further Al 13 has a large electron affinity of 3.4 eV close to that of a Cl atom (9). These analogies have prompted the concept that selected stable clusters could mimic the electronic behavior of elemental atoms and be classified as superatoms forming a third dimension of the periodic table (10-21). Because the properties of clusters change with size and composition, the superatoms offer the prospect of serving as the building blocks of nanomaterials with tunable characteristics (16,18).The electronic orbitals in superatoms, although resembling those in real atoms in shape, do spread over multiple atoms. This affects the way in which the electrons fill the shells because of two competing effects. Hund's rule favors high spin states in open shell systems stabilized by exchange coupling, and indeed higher spin multiplicities have been seen in some clusters (22) and even quantum dots spanning several nanometers (23). However, unlike the case of atoms, small clusters can undergo structu...

First-principles density functional calculations reveal that aluminum can form planar chains in zigzag and ladder structures. The most stable one has equilateral triangular geometry with four nearest neighbors; the other stable zigzag structure has wide bond angle and allows for two nearest neighbors. An intermediary structure has the ladder geometry and is formed by two strands. All these planar geometries are, however, more favored energetically than the linear chain. We found that by going from bulk to a chain the character of bonding changes and acquires directionality. The conductance of zigzag and linear chains is 4e^2/h under ideal ballistic conditions.Comment: modified detailed version, one new structure added, 4 figures, modified figure1, 1 tabl

Structure and electronic properties of neutral and cationic pure and Ni-doped Ge clusters containing 1-20 Ge atoms are calculated within the framework of linear combination of atomic orbitals density functional theory. It is found that in clusters containing more than 8 Ge atoms the Ni atom is absorbed endohedrally in the Ge cage. Relative stability of Ni-doped clusters at different sizes is studied by calculating their binding energy, embedding energy of a Ni atom in a Ge cluster, highest-occupied molecular orbital to lowest-unoccupied molecular orbital gap, and the second-order energy difference. Clusters having 20 valence electrons turn out to be relatively more stable in both the neutral and the cationic series. There is, infact, a sharp drop in IP as the valence electron count increases from 20 to 21, in agreement with predictions of shell models. Relevance of these results to the designing of Ge-based superatoms is discussed.