The discovery of carbon fullerene cages and their solids opened a new avenue to build materials from stable cage clusters as “artificial atoms” or “superatoms” instead of atoms. However, cage clust...

Endohedrally Doped Cage Clusters

Magnetic properties of atomic clusters and endohedral metallofullerenes

The TM-doped Si-based semiconductor clusters have aroused increased attention in a lot of fields. Here, we have performed a structural search of the global minimum for neutral and anionic Sin and L...

Probing the Structural and Electronic Properties of Neutral and Anionic Lanthanum-Doped Silicon Clusters

The initial stages of water adsorption on the Pd(111) and Ru(0001) surfaces have been investigated experimentally by Scanning Tunneling Microscopy in the temperature range between 40 K and 130 K, and theoretically with Density Functional Theory (DFT) total energy calculations and STM image simulations. Below 125 K water dissociation does not occur at any appreciable rate and only molecular films are formed. Film growth starts by the formation of flat hexamer clusters where the molecules bind to the metal substrate through the O-lone pair while making H-bonds with neighboring molecules. As coverage increases, larger networks of linked hexagons are formed with a honeycomb structure, which requires a fraction of the water molecules to have their molecular plane perpendicular to the metal surface with reduced water-metal interaction. Energy minimization favors the growth of networks with limited width. As additional water molecules adsorb on the surface they attach to the periphery of existing islands, where they interact only weakly with the metal substrate. These molecules hop along the periphery of the clusters at intermediate temperatures. At higher temperatures they bind to the metal to continue the honeycomb growth. The water-Ru interaction is significantly stronger than the water-Pd interaction, which is consistent with the greater degree of hydrogen-bonded network formation and reduced water-metal bonding observed on Pd relative to Ru.

Metal-and hydrogen-bonding competition during water absorption on Pd(111) and Ru(0001)

Stimulated by the recent fascinating finding of all-boron fullerene B40 (Zhai et al. in Nat Chem 6:727–731, 2014), we systematically investigated the structures, stabilities and electronic properties of its endohedral derivatives M@B40 (M = Sc, Y, La) by means of density functional theory computations. The binding energies of M@B40 are closely comparable with the classical M@C
 2v
 (9)–C82 family, suggesting the considerable possibility to experimentally achieve these endohedral borofullerenes. The paramagnetic M@B40 molecules can easily form stable dimers with quenched magnetism, which could be avoided by exohedral functionalization and promise potential applications in the design of nanodevices. Furthermore, the infrared absorption spectra and 11B nuclear magnetic resonance spectra were computed to assist future experimental characterization.

Computational investigation on the endohedral borofullerenes M@B 40 (M = Sc, Y, La)

First-principles calculations have been conducted to systemically investigate the stability and magnetic properties of 3d and 4d transitional-metal (TM) atoms doped in the BnNn (n=12,16,20,24,28) cages. Among those cages, the B24N24 is the optimal one for encapsulating 3d and 4d TM atoms according to the computed heat of formation. Inside B24N24 cage, 3d and 4d TM dopants belonging to the same group in the Periodic Table exhibit similar magnetic behaviors. Most of the 3d and 4d TM atoms remain magnetic after doped in the B24N24 cage except for Ni, Zr, and Pd. The magnitudes of the remaining moments for 3d (except for Sc, Ti, and V) and 4d dopants are reduced from those of free atoms. The energy gaps are localized at the doped transition metal atoms. Encapsulations of two TM atoms inside the B24N24 cage were also considered.

Stability and magnetic properties of transition metal atoms endohedral BnNn (n=12-28) cages.

Following the recent work of decomposing the total dipole moment and polarizability of a homogeneous system into site-specific contributions, we extend the study to the heterogeneous systems of iron-doped Sin (n = 1-14) clusters by introducing a weighting function. The structure-∕shape- and size-specific aspects of the dipole moments and polarizabilities of SinFe (n = 1-14) clusters are analyzed and compared with pure silicon clusters. It is shown that the polarizabilities associated with the individual constituent atoms vary considerably with the structure∕shape of the cluster and the location of the atom or site within a given structure. For atoms at peripheral sites, the polarizabilities are substantially larger than atoms at the interior sites, and the more peripheral an atom is, the larger is its polarizability. The polarizability of the Fe atom in SinFe clusters decreases as the cluster size increases. This is related to the position of Fe atom in SinFe clusters and indicates significant screening of the interior of the cluster by its surface. The correlation between the anisotropy of the total polarizability and the anisotropy of the cluster shape is also analyzed. Comparing with pure Sin clusters, the polarizabilities of Si atoms are increased after Fe atom doping. The structures are more compact for SinFe than the same sizes of Sin +1 clusters and the polarizabilities of SinFe are smaller than Sin +1 for the sizes of n = 7-14.

Site-specific analysis of dipole polarizabilities of heterogeneous systems: iron-doped Si(n) (n = 1-14) clusters.

Density functional theory calculations have been carried out to investigate 3d, Pd and Pt transition metal (TM) atoms exohedrally and endohedrally doped B80 fullerene. We find that the most preferred doping site of the TM atom gradually moves from the outer surface (TM = Sc), to the inner surface (TM = Ti and V) and the center (TM = Cr, Mn, Fe and Zn), then to the outer surface (TM = Co, Ni, Cu, Pd, and Pt) again with the TM atom varying from Sc to Pt. From the formation energy calculations, we find that doping TM atom can further improve the stability of B80 fullerene. The magnetic moments of doped V, Cr, Mn, Fe, Co and Ni atoms are reduced from their free-atom values and other TM atoms are completely quenched. Charge transfer and hybridization between 4s and 3d states of TM and 2s and 2p states of B were observed. The energy gaps of TM@B80 are usually smaller than that of the pure B80. Endohedrally doped B80 fullerene with two Mn and two Fe atoms were also considered, respectively. It is found that the antiferromagnetic (AFM) state is more energetically favorable than the ferromagnetic (FM) state for Mn2- and Fe2@B80. The Mn and Fe atoms carry the residual magnetic moments of ~ 3 μB and 2 μB in the AFM states.

Density functional theory study of transition metals doped B80 fullerene

Multistep dissociative chemisorption reactions of water with Pd4 and Pd7 clusters were studied using density functional theory. The adsorption energies and referred adsorption sites from water molecule (H2O) to partially dissociative (H2+O and OH+H), then to fully dissociative (O+H+H) configurations are carefully determined. It is found that the adsorption energies of three dissociative reactions are 5–6 times larger than that of water molecule. Atop sites of Pd4 and Pd7 clusters are found to be the most stable sites for the adsorbed H2O molecule. For the coadsorption cases of partially and fully dissociated products, H2 and OH molecules preferably tend to bind at the low coordination (atop or bridge) sites, and O and H atoms prefer to adsorb on the high coordination (hollow) sites. It is also found that the most favorable adsorption sites for the molecular adsorbates (H2O, H2 and OH) are adjacent to the Pd atoms with the largest site-specific polarizabilities. Therefore, site-specific polarizability is a good predictor of the favorable adsorption sites for the weakly bound molecules. The different directions of charge transfer between the Pd clusters and the adsorbate(s) is observed. Furthermore, the processes of the adsorption, dissociation, and the dissociative products diffusion of H2O are analyzed.

Li Ma

Papers

Stability and magnetic properties of transition metal atoms endohedral BnNn (n=12-28) cages.

Site-specific analysis of dipole polarizabilities of heterogeneous systems: iron-doped Si(n) (n = 1-14) clusters.

Density functional theory study of transition metals doped B80 fullerene

Multistep reactions of water with small Pdn clusters: A first principles study