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Mass spectrometry was used to observe the reactions between Y−Co heteronuclear metal carbide cluster anions Y1‐3CoC1,2− and N2 at room temperature. Y2CoC1,2− can produce Co ejection products, in which Y2CoC− also has N2 association products; YCoC2− and Y3CoC− only generate N2 association products, while YCoC− and Y3CoC2− are inert to N2. Detailed reaction pathways were obtained through density functional theory calculations, which reasonably explain the experimental phenomena. Co is superior to Y as the electrophilic reaction site in the clusters and is the preferential initial adsorption site for N2. Some crucial steps were identified, including N−N dissociation, CC−N formation, C−CN dissociation, and C−N formation. The energy barriers of these steps are closely related to the coordination mode of N/N2 and C/C2 in clusters. Two indicators, the N−N bond length and the Mayer bond order, were utilized to describe the activation degree of the N−N bond. Analyses on the density of states and the frontier molecular orbitals reveal the electronic structures of key intermediates for N−N dissociation. The reaction mechanisms of N2 activation on Y−Co carbide clusters obtained may lay a preliminary foundation for the further development of catalysts for nitrogen reduction reaction (NRR). [ABSTRACT FROM AUTHOR]

Rare earth elements have high chemical reactivity, and doping them into semiconductor clusters can induce novel physicochemical properties. The study of the physicochemical mechanisms of interactions between rare earth and tin atoms will enhance our understanding of rare earth functional materials from a microscopic perspective. Hence, the structure, electronic characteristics, stability, and aromaticity of endohedral cages MSn16− (M = Sc, Y, La) have been investigated using a combination of the hybrid PBE0 functional, stochastic kicking, and artificial bee colony global search technology. By comparing the simulated results with experimental photoelectron spectra, it is determined that the most stable structure of these clusters is the Frank–Kasper polyhedron. The doping of atoms has a minimal influence on density of states of the pure tin system, except for causing a widening of the energy gap. Various methods such as ab initio molecular dynamics simulations, the spherical jellium model, adaptive natural density partitioning, localized orbital locator, and electron density difference are employed to analyze the stability of these clusters. The aromaticity of the clusters is examined using iso-chemical shielding surfaces and the gauge-including magnetically induced currents. This study demonstrates that the stability and aromaticity of a tin cage can be systematically adjusted through doping. [ABSTRACT FROM AUTHOR]

The traditional methylammonium lead iodide perovskite (MAPbI3) is not stable under humid conditions, which limits its application. In this work, a new type of system is designed by replacing two MA cations of MAPbI3 with a chain-like divalent organic cation lying on the surface. Density functional theory calculations are performed to study the geometric and electronic properties of this kind of novel system, such as the hydrogen bonding, energy bands, and optical properties. Three types of divalent cations have been tested, MA(CH2)3MA, MA(C6H4)MA, and MA(C4H2S)MA, denoted as ProDMA, PhDMA, and ThDMA, respectively. It is found that all three divalent cations can improve the thermal and moisture stability of perovskite materials. In particular, ProDMA, without a ring structure in the middle of the chain, has the most suitable size to fill into the available space on the surface where two MA cations are removed, and the corresponding system has the highest stability, especially for water-resistance. At the same time, the performance of the optical absorption and the power conversion efficiency are similar to that of the pristine MAPbI3. This work suggests a promising strategy to improve the stability of perovskite materials by using divalent cations as the protective layer. [ABSTRACT FROM AUTHOR]

Structures of stoichiometric (La2O3)n (n = 1-6) clusters have been systematically studied by theoretical calculations. Global minimum structures for these clusters are determined by genetic algorithm based global optimizations at density functional level. The ground state structure for La6O9 was found to be highly symmetric with point group Oh and the centered oxygen atom has the coordination number as large as six, which is the same as the highest coordination number of oxygen atoms in bulk La2O3. Analysis of the binding energies shows that La6O9 has a high stability among the studied clusters. The energies of the highest occupied/lowest unoccupied molecular orbitals, vertical ionization energy, and vertical electron affinity of each cluster are provided. Electronic structure of La6O9 is discussed by analysis of the frontier molecular orbitals and unpaired spin density distributions of charged clusters. [ABSTRACT FROM AUTHOR]

The ability to activate methane differs appreciably for different transition metals, and it is attractive to find the most suitable metal for the direct conversion of methane to value-added chemicals. Herein, we performed a comparative study on the reactions of CH4 with Au2+, AuRh+ and Rh2+ cations by mass-spectrometry based experiments and DFT-based theoretical analysis. Different reactivity has been found for these cations: Au2+ has the lowest reactivity, and it can activate methane but only produce H–Au2–CH3+ without H2 release; Rh2+ has the highest reactivity, and it can produce both carbene-type Rh2–CH2+ and carbyne-type H–Rh2–CH+ with H2 release; AuRh+ also has high reactivity to produce only AuRh–CH2+ with H2, avoiding the excessive dehydrogenation of CH4. Our theoretical results demonstrate that Rh is responsible for the high reactivity, while Au leads to selectivity, which may be caused by the unique intrinsic bonding properties of the metals. [ABSTRACT FROM AUTHOR]

The side‐on‐end‐on coordination of N2 can be very important to activate and functionalize this very stable molecule. However, such coordination has rarely been reported. This study reports a gas‐phase species (a polynuclear vanadium nitride cluster anion [V5N5]−) that can capture N2 efficiently (12 %), and the quantum chemistry modelling suggests an unusual side‐on‐end‐on coordination. The cluster anions were generated by laser ablation and the reaction with N2 has been characterized by mass spectrometry, photoelectron imaging spectroscopy, and density functional theory calculations. The back‐donation interactions between the localized d–d bonding orbitals on the low‐coordinated dual metal (V) sites and the antibonding π* orbitals of N2 are the driving forces to adsorb N2 with a high binding energy (about 2.0 eV). [ABSTRACT FROM AUTHOR]