Jaakko Akola

A unified view of ligand-protected gold clusters as superatom complexes

Synthesis, characterization, and functionalization of self-assembled, ligand-stabilized gold nanoparticles are long-standing issues in the chemistry of nanomaterials. Factors driving the thermodynamic stability of well documented discrete sizes are largely unknown. Herein, we provide a unified view of principles that underlie the stability of particles protected by thiolate (SR) or phosphine and halide (PR3, X) ligands. The picture has emerged from analysis of large-scale density functional theory calculations of structurally characterized compounds, namely Au102(SR)44, Au39(PR3)14X6−, Au11(PR3)7X3, and Au13(PR3)10X23+, where X is either a halogen or a thiolate. Attributable to a compact, symmetric core and complete steric protection, each compound has a filled spherical electronic shell and a major energy gap to unoccupied states. Consequently, the exceptional stability is best described by a “noble-gas superatom” analogy. The explanatory power of this concept is shown by its application to many monomeric and oligomeric compounds of precisely known composition and structure, and its predictive power is indicated through suggestions offered for a series of anomalously stable cluster compositions which are still awaiting a precise structure determination.

On the Structure of Thiolate-Protected Au25

Density functional theory is used to explore the structure of Au25(RS)18. The preferred structure consists of an icosahedral Au13 core protected by 6 RS-Au-RS-Au-RS units. The enhanced stability of the structure as an anion is found to originate from closure of an eight-electron shell for delocalized Au(6s) electrons. The evaluated XRD pattern and optical spectra are in good agreement with experimental data.

Photoelectron spectra of aluminum cluster anions: Temperature effects and ab initio simulations

Photoelectron(PES) spectra from aluminum cluster anions, Aln- (12 < n < 15), at various temperature regimes, were studied using ab initio molecular dynamics simulations and experimentally. The calculated PES spectra, obtained via shifting of the simulated electronic densities of states by the self-consistently determined values of the asymptotic exchange-correlation potential, agree well with the measured ones, allowing reliable structural assignments and theoretical estimation of the clusters temperatures.

Density functional study of alkali-metal atoms and monolayers on graphite (0001)

Alkali-metal atoms (Li, Na, K, Rb, Cs), dimers, and

Edge-dependent selection rules in magic triangular graphene flakes

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Electronic shell and supershell structure in graphene flakes

monolayers on a graphite (0001) surface have been studied using density functional theory, pseudopotentials, and a periodic substrate. The adatoms bind at the hollow site (graphite hexagon), with Li lying closest to

Structure and bonding in the ubiquitous icosahedral metallic gold cluster Au144(SR)60

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IONIZATION POTENTIAL OF ALUMINUM CLUSTERS

and Cs farthest

Aluminum cluster anions: Photoelectron spectroscopy and ab initio simulations

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On the Structure of a Thiolated Gold Cluster: Au44(SR)282−†

from the surface. The adsorption energies range between 0.55 and