Reactivity and Photoionization Studies of Bimetallic Cobalt−Manganese Clusters

Abstract

The reactivity of selected Co n Mn m (8 ≤ m + n ≤ 23) clusters with N2 and the vertical ionization potentials (IPs) of selected Co n Mn m (8 ≤ m + n ≤ 31) clusters have been measured. No obvious correlation is found between the reactivities and the IPs. Inferences about cluster structure may be made from the nitrogen uptake data. In particular, whereas pure cobalt clusters tend to adopt structures having bulk packing, incorporation of manganese atoms into the cluster shifts the relative energies of close-lying isomers to favor an icosahedral growth sequence. For many cluster sizes, the maximum number of nitrogen molecules adsorbed on a cluster at −80 °C is equal to the number of cobalt atoms on the surface of the cluster, thereby giving insight into the cluster structure and the locations of the individual cobalt and manganese atoms in these bimetallic species.

Magnetism and chemical ordering in binary transition metal clusters

“…20,21 In order to systematically explore the effect of chemical ordering and composition on the cluster properties, we focus on closed-shell icosahedra with 13 and 55 atoms, which are found to be particularly stable for the TM clusters considered here. 6,22 However, there are still 164 possibilities to distribute two kinds of atoms over the sites of a 13-atom icosahedron. In addition, many different spin multiplicities had to be taken into account for each of these homotopes.…”

“…Today it has become feasible to conduct experiments in which some of these properties are measured on an atomic level. [6][7][8] In the case of Co-Mn, it could be shown recently that the clusters possess different magnetic properties than bulk Co-Mn: While in the latter, on the Co-rich side, the moment decreases with increasing Mn concentration x Mn , an increase is found for the clusters. 8 In contrast to that, the behavior of clusters matches that of the volume material in the Co-V system.…”

First-principles investigations of the structural, electronic, and magnetic properties of Pt13−nNin clusters

“…The structural, electronic and magnetic properties of Pt 13Àn Ni n clusters are studied in detail. In order to systematically explore the effect of composition on the cluster properties, we focus on icosahedral (I h ) configuration in this paper, which are found to be particularly stable for transition metal clusters with 13 atoms [24,25]. Firstly, Pt 13Àn Ni n clusters are optimized to get the lowest-energy configuration based on the binding energies and segregation energies of these clusters.…”

Magnetic Enhancement in Cobalt-Manganese Alloy Clusters

“…Here, we present magnetic measurements on Co N Mn M and Co N V M clusters, for N 60 and M N=3. The photoionization thresholds as well as reactivities were studied in molecular beams [13,14], but their magnetic properties have not been reported. The experimental method used here is described elsewhere [15,16].…”