The structural and electronic properties of NbSi_n^−/0(n = 3–12) clusters: anion photoelectron spectroscopy and ab initio calculations

Abstract

Niobium-doped silicon clusters, NbSi (n = 3-12), were generated by laser vaporization and investigated by anion photoelectron spectroscopy. The structures and electronic properties of NbSi anions and their neutral counterparts were investigated with ab initio calculations and compared with the experimental results. It is found that the Nb atom in NbSi prefers to occupy the high coordination sites to form more Nb-Si bonds. The most stable structures of NbSi are all exohedral structures with the Nb atom face-capping the Si frameworks. At n = 8, both the anion and neutral adopt a boat-shaped structure and the openings of the boat-shaped structures remain unclosed in NbSi clusters. The most stable structure of the NbSi anion is endohedral, while that of neutral NbSi is exohedral. The global minima of both the NbSi anion and neutral NbSi are D symmetric hexagonal prisms with the Nb atom at the center. The perfect D symmetric hexagonal prism of NbSi is electronically stable as it obeys the 18-electron rule and has a shell-closed electronic structure with a large HOMO-LUMO gap of 2.70 eV. The molecular orbital analysis of NbSi suggests that the delocalized Nb-Si ligand interactions may contribute to the stability of the D symmetric hexagonal prism. The AdNDP analysis shows that the delocalized 2c-2e Si-Si bonds and multicenter-2e NbSi bonds are important for the structural stability of the NbSi anion.

Structural Determination and Bonding Properties of Gas-Phase Ternary [O, Ta, 2C]− Anions

“…The experimental VDE and ADE of OTaC 2 – are obtained to be 2.85 ± 0.08 and 2.58 ± 0.08 eV, respectively. The measured details of experimental VDEs and ADEs can be found elsewhere …”

Structural evolution and bonding properties of BSin−/ (n = 4–12) clusters: Size-selected anion photoelectron spectroscopy and theoretical calculations

“…The HOMOs are all doubly occupied, and the LUMO is higher in energy than the HOMO by 3.27 eV, although the previous investigations have revealed that the HOMO-LUMO gap calculated with the B3LYP functional is more overestimate than that obtained from the other functional (BP86) by ∼1.00 eV. [67][68][69] This indicates that the BSi 11 − anion has a shell-closed electronic structure with a large HOMO-LUMO gap. The HOMO is a Si-Si σ orbital with bonding characters, mainly composed by the 3p orbitals of Si atoms.…”

Structural Evolution of B2Sin–/0 (n = 3–12) Clusters: Size-Selected Anion Photoelectron Spectroscopy and Theoretical Calculations

“…The previous photoelectron spectroscopy and photoelectron imaging experiments combined with theoretical calculations suggested that the ground-state structures of Si 5 2– , Si 5 – , and Si 5 clusters are trigonal bipyramid with D 3h symmetry, and Si 5 five-membered ring geometric structure is not stable. − Interestingly, here, we found that the Si 5 five-membered rings can be stabilized by the B atoms, thus, 10 Si atoms are able to form two Si 5 rings to encapsulate the B atoms in B 2 Si 10 –/0 . It is also interesting to note that two Si 6 six-membered rings can sandwich a transition metal atom such as Cr, V, or Nb, to form a hexagonal prism or distorted hexagonal prism structures. − Although two Si 5 five-membered rings are able to sandwich a B 2 unit in B 2 Si 10 –/0 , the sandwich of B 2 by two Si 6 six-membered rings in B 2 Si 12 –/0 is not stable. This indicates that the B 2 unit is capable to stabilize the Si 5 rings rather than the Si 6 rings.…”