Ab-initio Study of Small Silver Nanoclusters (original) (raw)
Related papers
2020
Our article is a systematic study toward understanding the mechanism of silver cluster formation. We calculated optical spectra of ultra-small silver clusters using time-dependent density functional theory (TDDFT) and compared our results with time-resolved UV-Vis spectra obtained from pulse radiolysis experiments during early stages of cluster formation. This comparative study indicates that the formation mechanism of silver clusters occurs through both monomer and ion addition growth pathways. Also, we calculated free energy of formation of small cationic and neutral clusters using density functional theory (DFT) which shows the thermodynamic stability of cationic clusters. In a conventional experimental system with the common reducing agents, the formation of cationic clusters is kinetically favored owing to the dominance of charged ions relative to neutral atoms in the system. While we show the stability of small cationic clusters relative to neutral clusters, collectively, we d...
Journal of Physical Chemistry A, 2007
Low-lying equilibrium geometric structures of Al n N (n ϭ 1-12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spinpolarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static dipole polarizabilities are calculated for the ground-state structures within the GGA. It is observed that symmetric structures with the nitrogen atom occupying the internal position are lowest-energy geometries. Generalized gradient approximation extends bond lengths as compared with the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within the GGA. The stability analysis based on the energies clearly shows the Al 7 N cluster to be endowed with special stability.
Ab initio calculations of structural and electronic properties of small silver bromide clusters
Journal of Chemical Physics, 1999
Ab initio configuration interaction ͑CI͒ calculations are performed to study the ground state of small neutral and singly charged silver bromide clusters Ag n Br p (Ϯ) (n,pр2). The results are obtained at complete active space self-consistent field and also at variational plus second order perturbational multireference CI ͑MRPT2͒ levels of approximation. We discuss more particulary the structural properties and the stability of the lowest isomers. Adiabatic and vertical ionization potentials and electron affinities have also been determined.
Nanoscale Molecular Silver Cluster Compounds in Gram Quantities
Angewandte Chemie International Edition, 2014
Dedicated to Professor Bernt Krebs on the occasion of his 75th birthday cluster compounds · gold · nanoparticles · silver · silver sulfide Fundamental knowledge of the intermediates between bulk materials (ionic, metallic) and molecular entities (e.g. clusters) is essential for the development of nanotechnology. The following interrelation exists between these areas, where the average oxidation number n of the metal atoms is a significant measure for the different metal-atom cluster types: "naked" metal-atom clusters (n = 0) stabilized with neutral ligands (PR 3 ), metalloid cluster compounds (0 n av n salt ) exhibiting even conductivity and superconductivity behavior, and saltlike cluster compounds which are mostly semi-conducting). The nanoscience of crystalline cluster compounds connect classical inorganic chemistry (bulk metals/bulk salts) with modern inorganic physical chemistry and physics.
Computational and Theoretical Chemistry, 2014
Density functional calculations using Wu and Cohen generalized gradient approximation functional are performed to investigate the structural properties and relative stability of silver doped gold clusters AgAu nÀ1 (n = 3-13). Low-lying energy structures include two dimensional and three dimensional geometries. Especially, for the lowest energy structures, the transition from planar to three dimensional structures is found to occur at n = 13 and the impurity Ag atom prefers to occupy higher coordination sites. The calculated binding energies, second-order differences in energies, dissociation energies and HOMO-LUMO energy gaps show pronounced odd-even oscillating behaviors, indicating that clusters with even number of atoms keep a higher relative stability than their neighboring odd-numbered ones. Particularly, the cluster AgAu 5 shows the strongest stability. Moreover, vertical ionization potential, vertical electronic affinity, and chemical hardness are discussed and compared in depth. The same odd-even oscillations are found.
Quantum Theoretical Study of Palladium and Silver Clusters
n and Ag n clusters (n = 2 thru 12). Transition-metal clusters can be useful for the study of quantum size effects and for formation of metallic states, and are ideal candidates for catalytic processes. Hybrid ab initio methods of quantum chemistry (particularly the DFT-B3LYP model) are used to derive optimal geometries for the clusters of interest. We compare calculated binding energies, bond-lengths, ionization potentials, electron affinities and HOMO-LUMO gaps for the clusters of the two different metals. Of particular interest are the comparisons of binding strengths at the three important types of sites: edge (E) sites, hollow sites (H) site and on-top (T) sites. Effects of crystal symmetries corresponding to the bulk structures for the two metals will also be investigated. The implications for the molecular dissociation of the H 2 and O 2 species will be considered.
Physical Review A, 2003
The formalism of second-order many-body perturbation theory has been applied to investigate the electronic and geometric structures of neutral, cationic, and anionic Ag n (nϭ5 -9) clusters. Hay-Wadt relativistic effective core potentials replacing the 28 core electrons and a Gaussian basis set have been used. Full geometry optimizations of topologically different clusters and clusters belonging to different symmetry groups have been carried out. The neutral silver clusters prefer planar geometry up to nϭ6 and the charged clusters prefer three-dimensional geometry from nϭ6. Binding energies, ionization potentials, electron affinities, and fragmentation energies of the optimized clusters have been compared with other experimental and theoretical results available in the literature. Based on different criteria, we predict the eight-atom silver cluster to be a magic-number cluster.
Molecular-dynamics simulations of silver clusters
Physica E: Low-dimensional Systems and Nanostructures, 1999
Structural stability and energetics of silver clusters, Agn (n = 3-177), have been investigated by molecular-dynamics simulations. An empirical model potential energy function has been used in the simulations. Stable structures of the microclusters with sizes n = 3-13 and clusters generated from FCC crystal structure with sizes n = 13-177 have been determined by molecular-dynamics simulation. Five-fold symmetry appears on the spherical clusters.
A Correlation Study of Small Silver Clusters
The European Physical Journal D, 2003
The formalisms of many body perturbation theory and coupled cluster theory have been used to study the electronic and geometric structures of neutral, cationic, and anionic small silver clusters. Hay-Wadt relativistic effective core potentials replacing the twenty-eight core electrons and a Gaussian basis set have been used. Topologically different clusters and clusters belonging to different symmetry groups have been identified and studied in detail. Full geometry optimizations have been carried out at four different correlated levels of theories. Ionization potentials, electron affinities, and fragmentation energies of the optimized clusters have been compared with other experimental and theoretical results available in the literature. No convergence problems are encountered at the various levels of correlated theories. This is noteworthy since it has been claimed in the literature that for d elements the MP series does not converge very well.
Density functional theory (DFT) calculations were carried out to explore the geometric, spectroscopic, and electronic properties of three magic silver clusters Ag n (n = 8, 18, and 20) in detail. The computed results show that the global minima of these clusters are compact, near-spherical structures, while other low-lying isomers exhibit oblate or prolate shapes. Vertical ionization energies for the low-lying isomers were also computed and assigned with respect to available experimental values. Although several isomers were predicted to have similar energies, their electronic and vibrational signatures were quite distinctive, meaning that they could be used as fingerprint signals to distinguish between isomers. In addition, the electronic structures of these systems were explored using the phenomenological shell model. Calculations for the coinage metal clusters M 20 (M = Cu, Ag, Au) indicated that the structures and properties of the Ag cluster are similar to those of the Cu cluster in that both Cu 20 and Ag 20 prefer a compact structure whereas Au 20 prefers to adopt a tetrahedral form.