Structure, bonding, and magnetism in manganese clusters

Abstract

We investigate the structures and magnetic properties of small Mn(n) clusters in the size range of 2-13 atoms using first-principles density functional theory. We arrive at the lowest energy structures for clusters in this size range by simultaneously optimizing the cluster geometries, total spins, and relative orientations of individual atomic moments. The results for the net magnetic moments for the optimal clusters are in good agreement with experiment. The magnetic behavior of Mn(n) clusters in the size range studied in this work ranges from ferromagnetic ordering (large net cluster moment) for the smallest (n=2, 3, and 4) clusters to a near degeneracy between ferromagnetic and antiferromagnetic solutions in the vicinity of n=5 and 6 to a clear preference for antiferromagnetic (small net cluster moment) ordering at n=7 and beyond. We study the details of this evolution and present a picture in which bonding in these clusters predominantly occurs due to a transfer of electrons from antibonding 4s levels to minority 3d levels.

Magnetic structure variation in manganese-oxide clusters

“…2,4,5 Mn 6 and Mn 7 are ferrimagnetic, 5,9 and there is a distinct transition from high-to low-spin configurations in Mn n clusters with n ≥ 7. 5 In all anionic clusters, Mn − n (n = 2-8), the preferred ordering is ferromagnetic. 7 The addition of a single oxygen into certain bare Mn clusters has also been considered.…”

“…[1][2][3][4][5][6][7][8] The magnetic ordering of the Mn 2 dimer is very sensitive to interatomic separation, [1][2][3] while clusters containing 3-5 Mn atoms are all predicted to have ferromagnetic ground states with magnetic moments of ∼5 μ B /atom. 2,4,5 Mn 6 and Mn 7 are ferrimagnetic, 5,9 and there is a distinct transition from high-to low-spin configurations in Mn n clusters with n ≥ 7. 5 In all anionic clusters, Mn − n (n = 2-8), the preferred ordering is ferromagnetic.…”

“…Mn 5 O and Mn 6 O were studied by Jones et al using a combination of negative-ion PES and quantum calculations. 11 They found that the ferromagnetic states of Mn 5 and Mn 6 are destabilized by the addition of oxygen, and the overall magnetic moment is reduced compared to pure Mn n clusters.…”

“…11 They found that the ferromagnetic states of Mn 5 and Mn 6 are destabilized by the addition of oxygen, and the overall magnetic moment is reduced compared to pure Mn n clusters. Another conclusion of this work was the identification of several nearly degenerate "isomags."…”

Chemical Bonding and Electronic Properties of the Co Adatom and Dimer Interacting with Polyaromatic Hydrocarbons

“…[22][23][24] There are several theoretical and experimental efforts devoted to understanding the structural, electronic, and magnetic properties of TM clusters. [25][26][27][28][29][30][31][32][33][34][35] In particular, Co clusters are one of the most important examples due to their magnetic properties [31][32][33][34][35][36] and their importance in the Fischer-Tropsch (FT) process. [37][38][39][40] Due to the high activity and long life time, 36 cobaltbased catalyst is currently the catalyst of choice for the conversion of syngas to liquid fuels in the FT process.…”