No abstract

The paramagnetic cluster [Cu Al ](Cp*) was obtained from the reaction of [CuMes] and [AlCp*] (Cp*=η -C Me ; Mes=mesityl). This all-hydrocarbon ligand-stabilized M magic atom-number cluster features a Mackay-type nested icosahedral structure. Its open-shell 67-electron superatom configuration is unique. Three unpaired electrons occupy weakly antibonding jellium states. The situation prefigures the formation of a conduction band, which is in line with the measured temperature-independent magnetism. Steric protection by twelve Cp* ligands suppresses the intrinsic polyradicalar reactivity of the Cu Al core.

On the basis of DFT results for a set of representative bulk, surface, and cluster systems, we determined a new embedded-atom potential for Pd/Au alloys. This embedded-atom approach accurately reproduces DFT properties of such alloy systems. We applied this potential in Monte Carlo simulations to study the effects of temperature and composition on the structure and bonding of Pd/ Au alloy nanoparticles up to 5 nm in diameter. We characterized the structure of those particles by evaluating the gold concentration at the surface and in the interior, the coordination numbers of atoms, the nature of Pd entities at the surface, and the number of suggested active sites for vinyl-acetate formation.

The focalization of elastic waves within a two dimensional gradient-index phononic crystal (GRIN PC) is numerically and experimentally investigated. The structure is formed by a square lattice of air holes in a silicon plate with transverse variation of holes’ diameters. The geometry and efficiency of focalization are computed with a finite element method. A non-contact laser-ultrasonic technique is used both to excite flexural Lamb waves and to monitor in situ the displacements field within the GRIN PC. The efficient subwavelength focusing is achieved and analyzed; furthermore, we describe the oscillatory behavior of focusing and show the relationship between the responses of waves in GRIN PC and the source intensity.