SmB₆^– Cluster Anion: Covalency Involving f Orbitals

Abstract

While boride clusters of alkali and transition metals have been observed and extensively characterized, so far little is known about lanthanide−boron clusters. Lanthanide−boride solids are intriguing, however, and therefore it is of interest to understand the fundamental electronic properties of such systems, also on the subnano scale. We report a joint experimental photoelectron spectroscopic and theoretical study of the SmB 6 − anion, iso-stoichiometric to the SmB 6 solida topological Kondo insulator. The cluster is found to feature strong static and dynamic electron correlations and relativistic components, calling for treatment with CASPT2 and up sixth-order Douglass−Kroll−Hess (DKH) relativistic correction. The cluster has a C 2v structure and covalent Sm−B bonds facilitated by f atomic orbitals on Sm, which are typically thought to be contracted and inert. Additionally, the cluster retains the double antiaromaticity of the B 6 2− cluster.

Dynamical Bonding Driving Mixed Valency in a Metal Boride

“…They all have the same cubic structures, but dramatically varying properties. [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] For example, EuB 6 and SmB 6 both have an anomalous peak in the specific heat, while for LaB 6 no such peak exists. T and p-sensitive magnetization, resistivity, and electronic phase transitions have been seen also in EuB 6 , GdB 6 , PrB 6 , and YbB 6 .…”

Exotic electronic structures of SmxCe3−xOy (x = 0-3; y = 2-4) clusters and the effect of high neutral density of low-lying states on photodetachment transition intensities

“…In addition, 4f -covalency with O 2p orbitals is also predicted (hatched red and gray), an effect previously reported by Bowen and co-workers in studies on SmB 6 − /SmB 6 . 86 These relative occupied orbital energies are evocative of the bulk band structure of Sm 2 O 3 , in which the 4f band is energetically embedded at the top of the VB. 87,88 Calculations on the lowest energy structure found for SmCe 2 O 4 − [ Fig.…”

TGMin: An efficient global minimum searching program for free and surface‐supported clusters

“…Lanthanide boron clusters are rarely studied before . The PrB 7 − cluster was the first observed lanthanide boron‐complex that was investigated by TGMin program .…”