Communication: Structure of magnetic lanthanide clusters from far-IR spectroscopy: ${\rm Tb}_n^+$ Tb n+ (n = 5−9)

Abstract

Small lanthanide clusters have interesting magnetic properties, but their structures are unknown. We have identified the structures of small terbium cluster cations Tb(n)(+) (n = 5-9) in the gas phase by analysis of their vibrational spectra. The spectra have been measured via IR multiple photon dissociation of their complexes with Ar atoms in the 50-250 cm(-1) range with an infrared free electron laser. Density functional theory calculations using a 4f-in-core effective core potential (ECP) accurately reproduce the experimental far-IR spectra. The ECP corresponds to a 4f(8)5d(1)6s(2) trivalent configuration of terbium. The assigned structures are similar to those observed in several other transition metal systems. From this, we conclude that the bonding in Tb clusters is through the interactions between the 5d and 6s electrons, and that the 4f electrons have only an indirect effect on the cluster structures.

Monoxides of small terbium clusters: A density functional theory investigation

“…74 Recently, the similarity of theoretical spectra to experimental spectra has been achieved for Tb n + (n = 5-9) clusters. 13 We follow this approach, i.e., in terms of the best fitting of our theoretical vibrational frequencies (the mostly intense peaks at 73.3, 71.4, and 76.2 cm −1 ) with the recently experimental values (109, 102, and 121 cm −1 ) 13 for Tb 5 + , Tb 6 + , and Tb 7 + clusters, respectively, and find that a scaling factor of 0.67 is appropriate for Tb n clusters. This treatment yields that our theoretical IR spectrum on Tb n clusters is compatible with the experimental findings within 5% of the individual central frequencies, i.e., relative positions of theoretical intense peaks are in the vicinity of each other of the experimental ones, and relative intensities match the experimental ones qualitatively well.…”

“…The optimized Cartesian coordinates in x; y;z in angstroms for all the represented structures in this paper are given as supplementary material. 67 It should be mentioned that although a large number of isomeric structures are obtained for each cluster, for the sake of simplicity, we only show three different low-lying representative structures in 13 O, two meta-stable structures, in analogy to the most stable structure in an icosahedral morphology yet having close energies (∆E = 0.2-0.5 eV), are discarded. Consequently, its second isomer in a HCP structure is higher in energy than the most stable structure by a large value of 2.0 eV.…”

“…In our previous works, this method has been used to treat transition metal (TM) clusters [45][46][47][48][49][50][51] and lanthanide clusters, 18,20,28 for which the lowest energy structures we obtained were positively confirmed by the subsequent works using the unbiased global optimizations. 13,[52][53][54][55][56][57] Following above approaches, we consider all possible configurations for small sizes (n = 2-7), but construct a large number of initial configurations for large sizes (n = [8][9][10][11][12][13][14] primarily at the additive and substitutive patterns from the low-lying structures of Tb n±1 , e.g., three different binding modes are intensively examined for the adsorption of oxygen atom: atop, bridge, and hollow sites. Furthermore, the lowlying structures analogous to other lanthanide oxide clusters and TM oxide clusters are chosen as the possible candidates.…”

“…1,2 Small clusters have been proposed as the good models for understanding their intrinsic properties at a microscopic scale. Up to now, Stern-Gerlach experiments on Pr, 3 Ho, 4 Tm, 4 Tb, [3][4][5] Gd, [5][6][7][8] and Dy clusters 5,[9][10][11] for their magnetic moments, photoionization spectra on Ce and Pr clusters for their ionization potentials (IPs), 12 as well as far-infrared (IR) vibrational spectroscopy on Tb n + (n = 5-9) clusters for their structures 13 have been already performed. Meanwhile, several theoretical works have been done on Ln n (Ln = Ce, Pr, Gd, Tb) clusters [14][15][16][17][18][19][20] to interpret these measured properties.…”

First-Principles Study of Structural, Electronic and Magnetic Properties of Metal-Centered Tetrahexahedral V15+ Cluster

“…Transition metal clusters have attracted a lot of attention because of their especially important roles in nanostructured material science [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ], which are quite different from those of individual atoms or bulk phase [ 10 , 11 ], and present a strong size dependence on their interesting physicochemical properties, e.g., optical [ 12 , 13 , 14 ], magnetic [ 15 , 16 ] and catalytic [ 17 , 18 , 19 ] properties, serving in various industrial application [ 20 ]. In particular, vanadium clusters are of special interest, due to their magnetic properties [ 21 , 22 , 23 , 24 ] and novel catalysis [ 25 , 26 ], which are closely related to their electronic structures.…”