Comparative DFT study of structure and magnetism of TMnOm (TM = Sc–Mn, n = 1–2, m = 1–6) Clusters

Abstract

A systematic theoretical study of the structural and magnetic properties of small transition metal oxide clusters TM_nO_m (TM = Sc, Ti, V, Cr and Mn; n = 1, 2; m = 1–6) has been carried out by using an ab initio density functional theory approach. The O atoms are partly molecularly adsorbed in O-rich and few-valence electron TM oxide clusters like ScO₃, TiO₃, Sc₂O_4–6, Ti₂O_5–6, and V₂O₆. The binding energy increases monotonously with increasing O atoms and decreases with the appearance of the peroxide unit, with the exception of ScO₃. The Sc-, Ti- and V- oxide clusters have a stronger binding than the Cr- and Mn-oxide ones. The magnetic properties are dependent on the TM element and on the density of O. The successive addition of an O atom to Mn₂ induces an odd–even magnetic oscillation from antiferromagnetic to ferrimagnetic and to nonmagnetic state. In the V-, Cr- and Mn-oxide clusters, the O atoms play a negligible role in the magnetism and they are generally antiferromagnetic when coupled with TM atoms, while the O atoms possess large magnetic moments in some Sc- and Ti- oxide clusters.