Cu cluster shell structure at elevated temperatures

Theoretical Study on the Aggregation of Copper Clusters on a Liquid Surface

The ground state structures of copper clusters with different sizes along with their aggregation have been systematic investigated using Amsterdam Density Functional (ADF) and Atomistix ToolKit (ATK) programs. On the basis of geometry optimization, some Cu clusters with more stable structures which were not reported previously have been revealed. In most cases, these Cu clusters prefer to adopt icosahedral structures which originate from the 13-atom icosahedron. It has also been demonstrated that the interaction between two Cu clusters is anisotropic, which is attributed to their charge distribution, especially the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of Cu clusters. Moreover, we have carried out the simulation of Cu clusters aggregation on the silicone oil substrate by means of Monte Carlo (MC) method, which shows good consistence with our previous experimental studies.

In-Situ High-Resolution Transmission Electron Microscopy Investigation of Overheating of Cu Nanoparticles

Synthesizing and functionalizing metal nanoparticles supported on substrates is currently the subject of intensive study owing to their outstanding catalytic performances for heterogeneous catalysis. Revealing the fundamental effect of the substrates on metal nanoparticles represents a key step in clarifying mechanisms of stability and catalytic properties of these heterogeneous systems. However, direct identification of these effects still poses a significant challenge due to the complicacy of interactions between substrates and nanoparticles and also for the technical difficulty, restraining our understanding of these heterogeneous systems. Here, we combine in situ high-resolution transmission electron microscopy with molecular dynamics simulations to investigate Cu nanoparticles supported on graphite and Cu₂O substrates, and demonstrate that melting behavior and thermal stability of Cu nanoparticles can be markedly influenced by substrates. The graphite-supported Cu nanoparticles do not melt during annealing at 1073 K until they vanish completely, i.e. only the sublimation occurs, while the Cu₂O-supported Cu nanoparticles suffer melting during annealing at 973 K. Such selective superheating of the Cu nanoparticles can be attributed to the adsorption of a thin carbon layer on the surface of the Cu nanoparticles, which helps guide further stability enhancement of functional nanoparticles for realistic applications.

Electric dipole polarizabilities of copper clusters

The static electric dipole polarizabilities of Cu(9)-Cu(61) have been measured via a molecular beam deflection method. The clusters display per-atom polarizabilities that decrease monotonically with size, from approximately 16 A(3) per atom Cu(9-10) to approximately 5 A(3) (Cu(45-61)). Absent are any discernible discontinuities or odd-even alternations due to electronic shell filling or electron pairing effects. For the smallest clusters, the experimental polarizabilities are approximately 3 times larger than those predicted classically for conducting ellipsoids, and approach the classical values only for clusters containing more than approximately 45 atoms.

Thermal quenching of electronic shells and channel competition in cluster fission

Experimental and theoretical studies of fission of doubly charged Li, Na, and K clusters in the low-fissility regime reveal the strong influence of electronic shell effects on the fission products. The electronic entropy controls the quenching of the shell effects and the competition between magic-fragment channels, leading to a transition from favored channels of higher mass symmetry to the asymmetric channel involving the trimer cation at elevated temperatures.