Ignacio L. Garzón

Chirality in Bare and Passivated Gold Nanoclusters

Detailed knowledge of the lattice structure, shape, morphology, surface structure, and bonding of bare and passivated gold clusters is fundamental to predict and understand their electronic, optical, and other physical and chemical properties. This information is essential to optimizing their utilization as novel nanocatalysts, 1 and as building-blocks of new molecular nanostructured materials, 2 with potential applications in nanoelectronics 3 and biological diagnostics. 4 An effective theoretical approach to determine gold cluster structures is to combine genetic algorithms and many-body potentials ~to perform global structural optimizations!, and first-principles density functional theory ~to confirm the energy ordering of the local minima!. Using this procedure we recently found many topologically interesting disordered gold nanoclusters with energy near or below the lowestenergy ordered isomer. 5‐ 8 The structures of these clusters

On the origin of the optical activity displayed by chiral-ligand-protected metallic nanoclusters.

Ligand-protected metallic clusters exhibit optical activity when chiral molecules are used as protecting units. Various mechanisms, such as the inherently chiral metallic cluster core, the dissymmetric field effect, and the chiral footprint model, have been proposed as possible explanations of the nonzero circular dichroism (CD) spectra found for these nanoscale materials. This communication presents a first-principles theoretical study of the CD spectrum of the [Au(25)(SR)(18)](-) cluster that was undertaken to gain insight into the physicochemical origin of the optical activity measured for the glutathione-protected [Au(25)(SG)(18)](-) cluster. The calculated CD spectrum of the cysteine-protected cluster, with R(cys) = C(beta)H(2)-C(alpha)H(NH(2))-COOH, shows good agreement with the experimental data obtained for the glutathione-protected cluster. Analysis of the calculated CD spectra of the peculiar two-shell metallic core and the two distinct thiolate-Au binding modes existing in the [Au(25)(SR(cys))(18)](-) cluster showed that the weak CD signal due to the slight distortion of cluster core is enhanced by the dissymmetric location of the ligands forming the Au-S binding modes. This result shows that the mechanisms proposed to explain the optical activity of chiral-ligand-protected metallic clusters cannot be differentiated but are acting concurrently. It is also predicted that the CD line shape should be highly sensitive to the orientation of the thiolate ligands forming the cluster protecting layer and to the stability of the thiolate-Au binding modes.

Ab initio study of small gold clusters

Abstract The most stable geometries (lowest energy configurations) as well as the lowest-lying isomers of Aun, n=2–6, clusters are determined through ab initio calculations of the cluster total energy. It is found that Hartree–Fock plus second-order perturbation method of Moller–Plesset combined with a double-zeta basis set and an 11 valence electrons relativistic pseudopotential provide reliable results for a qualitative and quantitative analysis of the structures. Two-dimensional planar configurations are obtained as the lowest energy structures for all the gold cluster sizes investigated. Vibrational frequencies for all the investigated isomers were obtained.

Negative heat capacity of sodium clusters

Heat capacities of

Low-symmetry structures of Au32Z (Z = +1, 0, -1) clusters.

{\mathrm{Na}}_{N},

Hybrid DNA-gold nanostructured materials: an ab initio approach

N=13,

Structural patterns of unsupported gold clusters

20, 55, 135, 142, and 147, clusters have been investigated using a many-body Gupta potential and microcanonical molecular-dynamics simulations. Negative heat capacities around the cluster meltinglike transition have been obtained for

MOLECULAR DYNAMICS STUDY OF THE AG6 CLUSTER USING AN AB INITIO MANY-BODY MODEL POTENTIAL

N=135,

Evaporation of Lennard-Jones clusters

142, and 147, but the smaller clusters