Stabilization of golden cages by encapsulation of a single transition metal atom

The smallest triple-ring tubular gold clusters M2@Au15 with M = Mo, W: stability, electronic properties and nonlinear optical response

The smallest triple ring tube-like gold clusters M2@Au15q with M = Mo, W and q = 1, 0, -1 are reported for the first time. Incorporation of an M2 dimer results in a remarkable modification of both atomic and electronic structures of the gold host. While the bare Au15 cluster exhibits a 3D cage shape, the doubly doped clusters M2@Au15 in all charge states are found to prefer a tubular form composed of three five-membered Au rings in an anti-prism arrangement and stabilized by an M2 unit placed inside the tube-like Au15 gold framework. The equilibrium geometry of both M2@Au15 and M2@Au15- is not much modified upon electron detachment from or attachment to their pure gold counterpart. The anion M2@Au15- with 28 itinerant electrons establishes an electron shell configuration of 1S21P61D102S21F8, in which the 1F shell splits into four different sub-levels. These stable clusters are thus not magic. Computed results on the first and second hyper-polarizability parameters of the doped clusters show a strong dependence on the charge. Overall, the neutral M2@Au15 is found to exhibit a particularly strong nonlinear optical (NLO) response. These clusters can also be extended to 1D nanowires, providing helpful guidance for the design of novel gold-based nanowires with rich optoelectronic properties.

Exploring the Structural and Electronic Properties of Niobium Carbide Clusters: A Density Functional Theory Study

This paper systematically investigates the structure, stability, and electronic properties of niobium carbide clusters, NbmCn (m = 5, 6; n = 1-7), using density functional theory. Nb5C2 and Nb5C6 possess higher dissociation energies and second-order difference energies, indicating that they have higher thermodynamic stability. Moreover, ab initio molecular dynamics (AIMD) simulations are used to demonstrate the thermal stability of these structures. The analysis of the density of states indicates that the molecular orbitals of NbmCn (m = 5, 6; n = 1-7) are primarily contributed by niobium atoms, with carbon atoms having a smaller contribution. The composition of the frontier molecular orbitals reveals that niobium atoms contribute approximately 73.1% to 99.8% to NbmCn clusters, while carbon atoms contribute about 0.2% to 26.9%.

Aromatic and magnetic properties in a series of heavy rare earth-doped Ge6 cluster anions

A series of pentagonal bipyramidal anionic germanium clusters doped with heavy rare earth elements,REGe 6 - (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), have been identified at the PBE0/def2-TZVP level using density functional theory (DFT). Our findings reveal that the centrally doped pentagonal ring structure demonstrates enhanced stability and heightened aromaticity due to its uniform bonding characteristics and a larger charge transfer region. Through natural population analysis and spin density diagrams, we observed a monotonic decrease in the magnetic moment from Gd to Yb. This is attributed to the decreasing number of unpaired electrons in the 4f orbitals of the heavy rare earth atoms. Interestingly, the system doped with Er atoms showed lower stability and anti-aromaticity, likely due to the involvement of the 4f orbitals in bonding. Conversely, the systems doped with Gd and Tb atoms stood out for their high magnetism and stability, making them potential building blocks for rare earth-doped semiconductor materials.

Investigation of Structures, Stabilities, and Electronic and Magnetic Properties of Niobium Carbon Clusters Nb7Cn (n = 1-7)

The geometrical structures, relative stabilities, and electronic and magnetic properties of niobium carbon clusters, Nb7Cn (n = 1-7), are investigated in this study. Density functional theory (DFT) calculations, coupled with the Saunders Kick global search, are conducted to explore the structural properties of Nb7Cn (n = 1-7). The results regarding the average binding energy, second-order difference energy, dissociation energy, HOMO-LUMO gap, and chemical hardness highlight the robust stability of Nb7C3. Analysis of the density of states suggests that the molecular orbitals of Nb7Cn primarily consist of orbitals from the transition metal Nb, with minimal involvement of C atoms. Spin density and natural population analysis reveal that the total magnetic moment of Nb7Cn predominantly resides on the Nb atoms. The contribution of Nb atoms to the total magnetic moment stems mainly from the 4d orbital, followed by the 5p, 5s, and 6s orbitals.

Making Sense of the Growth Behavior of Ultra-High Magnetic Gd2-Doped Silicon Clusters

The growth behavior, stability, electronic and magnetic properties of the Gd₂Si_n^- (n = 3-12) clusters are reported, which are investigated using density functional theory calculations combined with the Saunders 'Kick' and the Artificial Bee Colony algorithm. The lowest-lying structures of Gd₂Si_n^- (n = 3-12) are all exohedral structures with two Gd atoms face-capping the Si_n frameworks. Results show that the pentagonal bipyramid (PB) shape is the basic framework for the nascent growth process of the present clusters, and forming the PB structure begins with n = 5. The Gd₂Si₅^- is the potential magic cluster due to significantly higher average binding energies and second order difference energies, which can also be further verified by localized orbital locator and adaptive natural density partitioning methods. Moreover, the localized f-electron can be observed by natural atomic orbital analysis, implying that these electrons are not affected by the pure silicon atoms and scarcely participate in bonding. Hence, the implantation of these elements into a silicon substrate could present a potential alternative strategy for designing and synthesizing rare earth magnetic silicon-based materials.

A joint experimental and theoretical study on structural, electronic, and magnetic properties of MnGen - (n = 3-14) clusters

A systematic structure and property investigation of MnGe_n ^- (n = 3-14) was conducted by means of density functional theory coupled with mass-selected anion photoelectron spectroscopy. This combined theoretical and experimental study allows global minimum and coexistence structures to be identified. It is found that the pentagonal bipyramid shape is the basic framework for the nascent growth process of MnGe_n ^- (n = 3-10), and from n = 10, the endohedral structures can be found. For n = 12, the anion MnGe₁₂ ^- cluster probably includes two isomers: a major isomer with a puckered hexagonal prism geometry and a minor isomer with a distorted icosahedron geometry. Specifically, the puckered hexagonal prism isomer follows the Wade-Mingos rules and can be suggested as a new kind of superatom with the magnetic property. Furthermore, the results of adaptive natural density partitioning and deformation density analyses suggest a polar covalent interaction between Ge and Mn for endohedral clusters of MnGe₁₂ ^-. The spin density and natural population analysis indicate that MnGe_n ^- clusters have high magnetic moments localized on Mn. The density of states diagram visually shows the significant spin polarization for endohedral structures and reveals the weak interaction between the Ge 4p orbital and the 4s, 3d orbitals of Mn.

Laser ablation synthesis of metal-doped gold clusters from composites of gold nanoparticles with metal organic frameworks

Metal-doped gold clusters, mainly cages, are receiving rapidly increasing attention due to their tunable catalytic properties. Their synthesis is mostly based on complex procedures, including several steps. In this work, via adsorption of gold nanoparticles (AuNPs) from aqueous solution to MOF (metal organic frameworks) of M = Co, Cu, Ni, and Zn with various linkers the {AuNPs, MOF} composites were prepared. These composites were used for laser ablation synthesis (LAS) using a common mass spectrometer. Several series of positively and negatively charged Au_mM_n^+/− clusters were observed in mass spectra and their stoichiometry (m = 1–35, n = 1–5) was determined. For each dopant (Co, Cu, Ni, and Zn) ~ 50 different clusters were identified in positive, as well as in negative ion modes. About 100 of these clusters were proposed to be endohedral metal-doped gold cages (for m > 12). The developed approach represents a simple procedure for generating metal-doped gold clusters or endohedral metal-doped gold cages materials with potential applications in medicine and/or electronics.

{Nano-gold, iron(III)-1,3,5-benzene tricarboxylate metal organic framework (MOF)} nano-composite as precursor for laser ablation generation of gold-iron Aum Fen +/- (m = 1-35, n = 1-5) clusters. Mass spectrometric study

RATIONALE

Gold-iron bimetallic materials have applications in many fields, especially in nanotechnology and biomedicine. The chemistry of iron-doped gold clusters is still not fully understood but opens up the possibility of developing new materials, e.g. of gold cages doped with iron atoms. There have been several theoretical studies on these clusters but only a few experimental studies.

METHODS

Laser desorption ionisation (LDI) was used for the generation of Au-Fe bimetallic clusters via laser ablation (337 nm nitrogen laser) of the synthesised nano-composite {nano-gold; Fe(III) 1,3,5-benzene tricarboxylate}, i.e. {AuNPs, Fe-MOF}, while a quadrupole ion trap time-of-flight mass spectrometer, equipped with a reflectron, was used to acquire mass spectra.

RESULTS

A {AuNPs, Fe-MOF} nano-composite was prepared and found suitable for the LDI generation of Au_m Fe_n clusters. In addition to Au_m ^+/- (m = 1-35) clusters, a series of positively and negatively charged gold-iron Au_m Fe_n ^+/- clusters were generated. The mass spectra exhibited evidence for the clusters containing up to five iron atoms. In total, 113 binary Au_m Fe_n ^+/- clusters (m = 1-35, n = 1-5) were identified in the gas phase.

CONCLUSIONS

A synthesised {AuNPs, iron(III)-1,3,5-benzene tricarboxylate MOF} nano-composite was found suitable for the generation of many new gold-iron clusters and mass spectrometry was shown to be an efficient technique for the determination of the cluster stoichiometry. A broad series of over 100 bimetallic Au_m Fe_n clusters, some of them suggested to be gold cages doped with iron atoms (for m = 12 and higher), not only demonstrate a rich and complex chemistry, but also open wide possibilities of biomedical applications.

The stability, electronic, and magnetic properties of rare-earth doped silicon-based clusters

The rare-earth doped silicon-based clusters exhibit remarkable structural, physical, and chemical properties, which make them attractive candidates as building units in designing of cluster-based materials with special optical, electronic, and magnetic properties. The structural, stability, electronic, and magnetic properties of pure silicon Si_n + 1 (n = 1-9) and rare-earth doped clusters Si_nEu (n = 1-9) are investigated using the "stochastic kicking" (SK) global search technique combined with density functional theory (DFT) calculations. It was found that: 1) the ground state structures of pure silicon clusters tend to form compact structures rather than cages with the increase of cluster size; 2) the ground state structures for doped species were found to be additional or substitutional sites, and the rare-earth atoms tend to locate on the surface of the silicon clusters; 3) the average binding energy of the doped clusters increased gradually and exhibited the final phenomenon of saturation with the increase of clusters size. The average binding energy of doped clusters was slightly higher than that of pure silicon clusters of the same size, which indicated that the rare-earth atom encapsulated by silicon enhanced the stability of the silicon clusters to some degree; 4) the doped clusters have strong total magnetic moments, which mainly originated from the contribution of rare-earth atoms, whereas the contribution of silicon atoms were almost negligible. As the cluster size increased, the total magnetic moments of binary mixed clusters tended to be stable.