Interplay between bonding and magnetism in the binding of NO to Rh clusters

Abstract

We have studied the adsorption of NO on small Rh clusters, containing one to five atoms, using density functional theory in both spin-polarized and non-spin-polarized forms. We find that NO bonds more strongly to Rh clusters than it does to Rh(100) or Rh(111); however, it also quenches the magnetism of the clusters. This (local) effect results in reducing the magnitude of the adsorption energy, and also washes out the clear size-dependent trend observed in the non-magnetic case. Our results illustrate the competition present between the tendencies to bond and to magnetize, in small clusters.arXiv:0709.4365v1 [cond-mat.mtrl-sci]

Effective coordination as a predictor of adsorption energies: A model study of NO on Rh(100) and Rh/MgO(100) surfaces

“…Out of the six Rh atoms present in the unit cell, the spin polarization of each of the two Rh atoms to which N is attached is negligible, while the spin polarization of those atoms to which O is attached is reduced by about 81% and the spin polarization of the two Rh atoms which are furthest from the NO is reduced by about 28%. Similar effects have also been observed previously by us for NO adsorbed on small Rh clusters 33 and by Hass et al 34 in their studies of NO adsorption on a hypothetical monolayer of Rh atoms. Apart from the fact that the latter group of authors worked with a monolayer of Rh ͑i.e., there was no substrate͒, there are other differences between our calculations and theirs: they did the calculations for NO adsorbing in the VB geometry alone, fixed the Rh-Rh distance at the value for bulk Rh, and did not relax the coordinates of NO.…”

Electronic structure and thermochemical properties of neutral and anionic rhodium clusters Rhn, n=2–13. Evolution of structures and stabilities of binary clusters RhmM (M=Fe, Co, Ni; m=1–6)

“…Clusters of rhodium have been the subjects of continuing experimental and theoretical investigations due to interest in the catalytic properties of the metal. For example, Ghosh and coworkers [1] suggested that Rh clusters are good catalysts for NO reduction. Furthermore, the high activity of rhodium clusters and surfaces for the adsorption and decomposition of N 2 O, CO had been investigated by far-infrared multiple photon dissociation experiments and DFT calculations [2][3][4][5][6].…”

Magnetism in Simple Metal and 4d Transition Metal Clusters

“…Here I will only mention the most important aspects keeping in mind that magnetism is our primary focus. For Rh 5 , GGA and B3LYP calculations find the sextet and octet spin states in the square pyramid structure to be very close in energy [61,63,64,69,76]. The energy difference is only a few tens of meV.…”

“…But Bae et al [63] found the ground state to be a bent rhombus, with the angle of bent nearly 90 0 , in a septet state. Ghosh et al [76] also found the ground state to be a septet but a tetrahedron. These authors also found a quintet square, and a singlet tetrahedron.…”