The teetotum cluster Li2FeB14 and its possible use for constructing boron nanowires

Metalloborospherenes with a Stabilized Classical Fullerene-like Borospherene B40 Act as Nonlinear Optical Switches, Electron Reservoirs, Molecular Capacitors, and Molecular Reactors

Using a new method of η5-Li and η6-Mg atoms capping the faces of the classical fullerene-like borospherene Td B40, we theoretically predict an exohedral metalloborospherene Td Mg10Li12&B40 molecule. Remarkably, a newfangled endoexo cage isomerism is proposed. Further, embedding Mg atoms in the Td B40 cage forms endohedral derivatives. Due to the intramolecular pull-push electron transfer relay, these obtained molecules possess unequal multilayered and alternant spherical charge distribution. The outer is an excess electron layer, bringing a molecular nonlinear switch character and an electron reservoir behavior with strong electron-donating and -accepting abilities. The middle (Mg2+)10(Li+)12 and the outer layers together constitute an electric double layer, presenting the behavior of a molecular capacitor where the electronic charge-discharge process occurs in the outer excess electron layer. The inner part is an empty cage B4026- with a strong negative electric field. The valence electrons of the embedded Mg atoms are transformed into new excess electrons and added in the outer excess electron layer, also exhibiting the charging behavior of the molecular capacitor. Considering the chemical reaction in the inner cage, the embedded Mg atom is ionized, forming an Mg2+ cation and 2e under the strong negative electric field; meanwhile, 2e is powerfully pushed into the outer excess electron layer. This chemical process shows a generalized Coulomb explosion, and thus the exohedral metalloborospherene molecules with cage B4026- may act as molecular reactors. The new species mark the genesis of classical fullerene-like borospherene chemistry and stimulate their applications in molecular nonlinear optical and nanoelectronics.

The binary boron lithium clusters B12Lin with n = 1-14: in search for hydrogen storage materials

Molecular structures and properties of the binary clusters containing twelve boron atoms mixed with n lithium atoms, B₁₂Li_n with n = 1-14, were investigated using density functional theory with the TPSSh functional and the 6-311+G(d) basis set. Energetic parameters including relative energies, average binding energies and second-order energies of the entire series were predicted using the coupled-cluster theory (U)CCSD(T) in conjunction with the cc-pVTZ basis set. Several lowest-lying isomers were determined for each size B₁₂Li_n whose energies differ from each other by <3 kcal mol^-1, except for n = 1, 2 and 4 (≤5 kcal mol^-1), and particularly n = 8 (∼13 kcal mol^-1). Electronic structure and chemical bonding in some specific sizes such as B₁₂Li₄, B₁₂Li₈ and B₁₂Li₁₄ were analyzed in detail. We established the electron shells of some magic clusters such as the B₁₂Li₄ cone for which we proposed a mixed cone-disk electron shell model. Thanks to both the phenomenological shell and Clemenger-Nilsson models, B₁₂Li₈ which contains a specific set of shells of 44 valence electrons is a high stability species. The arrangement of Li atoms around a fullerene B₁₂ framework shows that the mixed B₁₂Li₈ emerges as the most suitable of this cluster series to adsorb molecular hydrogen. Up to 32 H₂ molecules can strongly be attached to the B₁₂Li₈ cluster which is thus predicted to be a realistic candidate for hydrogen storage material with gravimetric density reaching up to a theoritical limit of 26 wt%. Attachment of the fifth H₂ molecule to each Li atom of B₁₂Li₈ results in weaker average bonds but can give rise to a total of 40 H₂ molecules, corresponding to 30 wt% of hydrogen.

Theoretical Design of Novel Boron-Based Nanowires via Inverse Sandwich Clusters

Borophene has important application value, boron nanomaterials doped with transition metal have wondrous structures and chemical bonding. However, little attention was paid to the boron nanowires (NWs). Inspired by the novel metal boron clusters Ln₂B_n⁻ (Ln = La, Pr, Tb, n = 7–9) adopting inverse sandwich configuration, we examined Sc₂B₈ and Y₂B₈ clusters in such novel structure and found that they are the global minima and show good stability. Thus, based on the novel structural moiety and first-principles calculations, we connected the inverse sandwich clusters into one-dimensional (1D) nanowires by sharing B−B bridges between adjacent clusters, and the 1D-Sc₄B₂₄ and 1D-Y₂B₁₂ were reached after structural relaxation. The two nanowires were identified to be stable in thermodynamical, dynamical and thermal aspects. Both nanowires are nonmagnetic, the 1D-Sc₄B₂₄ NW is a direct-bandgap semiconductor, while the 1D-Y₂B₁₂ NW shows metallic feature. Our theoretical results revealed that the inverse sandwich structure is the most energy-favored configuration for transition metal borides Sc₂B₈ and Y₂B₈, and the inverse sandwich motif can be extended to 1D nanowires, providing useful guidance for designing novel boron-based nanowires with diverse electronic properties.