Nature of the interaction between rare gas atoms and transition metal doped silicon clusters: the role of shielding effects

Abstract

Mass spectrometry experiments show an exceptionally weak bonding between Si 7 Mn + and rare gas atoms as compared to other exohedrally transition metal (TM) doped silicon clusters and other Si n Mn + (n = 5-10) sizes. The Si 7 Mn + cluster does not form Ar complexes and the observed fraction of Xe complexes is low. The interaction of two cluster series, Si n Mn + (n = 6-10) and Si 7 TM + (TM = Cr, Mn, Cu, and Zn), with Ar and Xe is investigated by density functional theory calculations. The cluster-rare gas binding is for all clusters, except Si 7 Mn + and Si 7 Zn + , predominantly driven by short-range interaction between the TM dopant and the rare gas atoms. A high s-character electron density on the metal atoms in Si 7 Mn + and Si 7 Zn + shields the polarization toward the rare gas atoms and thereby hinders formation of short-range complexes.Overall, both Ar and Xe complexes are similar except that the larger polarizability of Xe leads to larger binding energies.Atomic clusters emerge as interesting materials in the size regime between single atoms and nanoparticles, whose properties are strongly influenced by confinement effects. Understanding of their size and composition dependent structures and properties is primordial for further usage. The interactions between clusters and rare gas (RG) atoms are of crucial importance in many experimental techniques. For example, RG complexes are used for action spectroscopy in cluster science due to the inherent weak interaction, 1 Ar titration and tagging have been used to obtain isomer-specific photoelectron spectra for 2D and 3D gold clusters 2,3 and isomer selective infrared (IR) spectra of niobium clusters. 4 In most experimental studies, it has been assumed that the RG atoms do not significantly influence the intrinsic structure and properties of the bare clusters, and are therefore called messenger or spectator atoms. A negligible influence of the RG atoms is inferred from their low adsorption energies and from insignificant differences in measured IR spectra of elemental clusters and their Ar-complexes, such as for V n + , 5 Nb n + , 6 Ta n + (n = 6-20), 7 Si n + (n = 6-21), 8 as well as for binary Si n V + and Si n Cu + (n = 6-11) clusters. 9 Nevertheless, such an assumption is not always applicable. Stronger cluster-RG interactions, which cause discernible changes in the IR spectra of the bare clusters, were observed for some Co n + , Au n , and doped Au n Y clusters. 10-12 Moreover, the RG tagging of some oxide clusters changes the energetic ordering of the isomers, in which case a low-energetic structural isomer, and thus not the ground state structure of the bare cluster, is probed in the experiment. 13 A simple electrostatic picture was put forward to explain the stronger influence of the RG atom, analogous to models often used to interpret the interaction of RG atoms with metal surfaces 14 or metal complexes. 15 Much effort has been devoted to reveal the nature of interaction between RG and metal surfaces 12,16 or metal-atom complexes. 14,17 There are a...

Argon tagging of doubly transition metal doped aluminum clusters: The importance of electronic shielding

“…A similar kind of electronic shielding was observed for singly transition metal doped silicon clusters, Si n TM + (n = 5 -10, TM = Cr, Mn, Cu and Zn), interacting with Ar [38], with the difference that for those silicon clusters the shielding was mainly due to s-electrons of the transition metal dopants, while here the shielding is caused by Rh d 𝑧 2 orbitals.…”

Hydrogen Chemisorption on Doubly Vanadium Doped Aluminum Clusters

“…Here, however, the decrease is seen after n = 15. A possible explanation could be that at this size, one of the vanadium atoms occupies an endohedral position, and the other is partially shielded, either geometrically [21] or electronically [22]. Understanding the size-dependence of the reactivity of transition metal (doped) clusters in the gas phase is generally not an easy task due to the possibility of low-lying geometric or electronic states (possibly even of a different multiplicity), whose potential energy surfaces (PES) during the reaction with hydrogen might cross that of the ground state.…”

Benchmarking density functional theory methods for modelling cationic metal–argon complexes

“…Beyond single atoms, studies have focused on the interaction of small clusters with noble gases [18]. For example, Fielicke and co-workers combined infrared spectroscopy with DFT calculations to investigate the interaction of bimetallic AunAgm + (n+m = 3-5) clusters with Ar [19,20], showing that the bonding strength of the clusters towards Ar decreases with Ag content.…”