Spin-polarized electronic structure of cobalt cluster anions studied by photoelectron spectroscopy

Abstract

The photoelectron spectra of Co−n (3≤n≤70) were measured at the photon energy of 4.025 eV by use of a XeCl excimer laser. For Co−n with n=3, 4, and 6, the geometric and electronic structures were obtained from the spectra in comparison with the calculated spectra by the spin-polarized DV-Xα method. The spectra observed are reproduced reasonably well by the calculation with postulating the most probable geometrical structures. It is revealed that the 3d band with the majority spin is separated by 1.0–2.8 eV from that with the minority spin; the former is completely filled while the latter is partly filled and extends above Fermi level. The magnetic moments and the average exchange energies of these cluster anions were estimated. For Co−n with n≥7, the observed electron affinity depends linearly on the reciprocal of the cluster radius and approach the work function of a cobalt metal, as n increases. Below n=6, the electron affinity deviates from the linear dependence. This finding indicates that a size-dependent transition in the electronic structure occurs at n≂7. The spherical conducting drop model suggests the presence of mobile electrons in Co−n with n≥7.

Localization and bandwidth of the 3d-orbitals in magnetic Ni and Co clusters

“…5) have been obtained using a waiting room for most effective cooling. The spectra exhibit more fine structure than the earlier measurements from Yoshida et al [30] indicating the importance of temperature for such kind of measurements. The spectra of the Ni n -clusters (e.g., Fig.…”

Structure, bonding, and magnetism of cobalt clusters from first-principles calculations

“…There is no experimental result available on the structure of neutral tetramer. However, Yoshida et al 33 predicted a tetrahedral structure with a bond length of 2.25 ± 0.2Å as the ground state for Co − 4 anion. The initial rectangular structure becomes a rhombus after optimization, which also has 10 µ B magnetic moment and lies 0.11 eV higher in energy from the ground state.…”

“…Present result is in agreement with previous theoretical studies, 12,16,30,34 and the octahedral structure is generally accepted as the most stable structure for Co 6 cluster. However, photoelectron spectroscopic study 33 predicted a pentagonal pyramid with bond distances ∼ 2.75 ± 0.1Å to be the most probable structure for Co − 6 anion cluster, i.e., the geometrical structure might strongly be correlated with the charged state of the cluster.…”

“…32 The bonding in Co + 3 cation is stronger than the neutral Co 3 as it is the case for dimer. 23 Yoshida et al 33 reported that Co…”

Chemical Bonding of Transition‐Metal Co13 Clusters with Graphene

“…In many experimental setups aimed to produce beams of clusters, charged clusters are produced [76][77][78][79][80]. In order to extend the validity of our conclusions, we carry out some calculations to determine whether the stability order between free isomers remains the same or not when working with charged clusters.…”