Ab Initio Study of Structure and Magnetism of Late Transition Metal Oxide TMnOm Clusters (TM = Fe, Co, Ni, n = 1, 2, m = 1–6)

Phys. Chem. Chem. Phys.

Belay

Bozhenko

et al. 2016

Geometrical and electronic structures of the 3d-metal oxide clusters (FeO), (CoO), and (NiO) are computed using density functional theory with the generalized gradient approximation in the range of 1 ≤ n ≤ 10. It is found that the cluster geometries are similar in the (FeO) and (CoO) series but noticeably different in the (NiO) series for several values of n. All of the lowest total energy states are found to possess relatively small spin multiplicities and are either antiferromagnetic or ferrimagnetic except for the states of (NiO), (NiO), (NiO), and (NiO), which are ferromagnetic. The computed polarizabilities per atom undergo a steep decrease when compared to the atomic values of the MO monomers (M = Fe, Co, and Ni). Surprisingly, the polarizability does not strongly depend on either M or n in all the considered series when n varies from 3 to 10. The binding energies per atom are the largest in the (FeO) series, followed by the binding energies of (CoO) and (NiO).

Section: Binding Energiessupporting

confidence: 82%

A comparative study of small 3d-metal oxide (FeO)_n, (CoO)_n, and (NiO)_n clusters

Phys. Chem. Chem. Phys.

Belay

Bozhenko

et al. 2016

“…28 Geometrical structures and total spin magnetic moments of the neutral (FeO) n clusters have been computed in the range of up to n = 16. 29,30 Geometrical structures of a number of neutral and ionic nonstoichiometric Fe n O m clusters were studied [31][32][33][34][35][36][37][38][39] 40 and Fe 12 O m (m = 1-20). 41 Larger Fe n O m clusters were studied 42,43 using both DFT and DFT+U methods using bulk-like geometries.…”

Section: Introductionmentioning

confidence: 99%

Effect of hydrogenation on the structure and magnetic properties of an iron oxide cluster

Belay

Phys. Chem. Chem. Phys.

et al. 2018

The structure and properties of the FeOH clusters (n = 0-18) are computed using the all-electron density functional theory with the generalized gradient approximation for the exchange-correlation potential. The ground state of FeO is found to be a singlet state having a bi-capped octahedron geometry. Upon hydrogenation, the octahedral framework of Fe is retained in FeOH up to n < 7, beyond which point the iron octahedron transforms into a cube. Hydrogen atoms are bound to oxygen atoms up to n = 12, but they bind to the faces of the Fe cube when n > 12. The total spin magnetic moment of a FeOH cluster is larger than 6 μ for 1 ≤ n ≤ 18, except for n = 8 and 10, where the lowest total energy states are antiferromagnetic singlets. The reason for this deviation from the general behavior in the FeOH series is attributed to the collective superexchange phenomenon. Surprisingly, the total spin magnetic moment of a FeOH cluster is found to be substantially larger than the total spin magnetic moment of the bare Fe cluster when n = 12-18. All of the FeOH clusters are stable with respect to an abstraction of a single hydrogen atom but are unstable toward the abstraction of an H dimer when n =10 and n = 14-18.

“…TMO-NP of late transition-metal elements (Fe, Co and Ni) have been extensively investigated both experimentally and theoretically [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Photoelectron spectroscopy (PES) [ 36 , 37 ] allows one to determine the most abundant stoichiometries and cluster products resulting after fragmentation of a parent cluster.…”

Section: Introductionmentioning

confidence: 99%

Tuning the Magnetic Moment of Small Late 3d-Transition-Metal Oxide Clusters by Selectively Mixing the Transition-Metal Constituents

et al. 2020

Transition-metal oxide nanoparticles are relevant for many applications in different areas where their superparamagnetic behavior and low blocking temperature are required. However, they have low magnetic moments, which does not favor their being turned into active actuators. Here, we report a systematical study, within the framework of the density functional theory, of the possibility of promoting a high-spin state in small late-transition-metal oxide nanoparticles through alloying. We investigated all possible nanoalloys An−xBxOm (A, B = Fe, Co, Ni; n = 2, 3, 4; 0≤x≤n) with different oxidation rates, m, up to saturation. We found that the higher the concentration of Fe, the higher the absolute stability of the oxidized nanoalloy, while the higher the Ni content, the less prone to oxidation. We demonstrate that combining the stronger tendency of Co and Ni toward parallel couplings with the larger spin polarization of Fe is particularly beneficial for certain nanoalloys in order to achieve a high total magnetic moment, and its robustness against oxidation. In particular, at high oxidation rates we found that certain FeCo oxidized nanoalloys outperform both their pure counterparts, and that alloying even promotes the reentrance of magnetism in certain cases at a critical oxygen rate, close to saturation, at which the pure oxidized counterparts exhibit quenched magnetic moments.