Characterization of Magnetic Series of Iron–Carbon Clusters Fe_nC^0,±1 (n ≤ 13)

Abstract

The evolution of structural and electronic properties of neutral and charged iron clusters doped with a single carbon atom, Fe n C0,±1 (n = 1–13) series, is studied in this work, which has been carried out throughout all-electron density functional calculations at the BPW91/6-311++G­(2d,2p) level of theory. The results indicate a redshift of the bands in the infrared spectra due to carbon–iron stretching because the cluster contains more iron atoms. The iron–carbon bond lengths and the iron–carbon–iron bond angle increase and the ionization energies decrease as the cluster size increases. Notably, the total spin multiplicity increases smoothly even with the inclusion of the carbon atom. Also, the spin from the additional carbon atom turns parallel in the larger species, contributing to the total magnetic moment. In the Fe6–9,12,13C0,±1 species, the carbon atom becomes tetravalent with a near-planar form. This unusual coordination between carbon and the iron core may be due to the lack of hybridization between the s and p orbitals of carbon and to the large iron–carbon bonds. The nearly straight iron–carbon–iron angles are due to the overlap, in occupied orbitals close to the highest occupied molecular orbital, among pure p orbitals and most of d orbitals of carbon and iron atoms, respectively.

Small Transition-Metal Mixed Clusters as Activators of the C–O Bond. FenCum–CO (n + m = 6): A Theoretical Approach

“…On the experimental side, the measured C–O stretching frequency of about 1865 cm –1 was attributed to CO bonded on atop sites, whereas twofold modes are expected to appear redshifted by 150–200 cm –1 . This observation is consistent with our results for Fe n Cu m CO, where the largest redshifted ν CO values were found for clusters rich in iron atoms and with a higher coordination of CO. , These features are fulfilled by the threefold coordination seen in the Fe 3 Cu 3 CO and Fe 6 CO species.…”

Synthesis and magnetic properties of sub-nanosized iron carbides on a carbon support

“…48 Additionally, the density functional theory studies have reported that the iron carbide clusters show the magnetic moment of ca. 1-3.5 m B atom Fe À1 , [30][31][32] which is consistent with those in this study. Therefore, with consideration of the magnetic moment and the Curie temperature, it was concluded that the magnetic behavior of the iron carbide cluster samples is derived from the carbides themselves, and not from impurities.…”

“…2 nm, 7,16 aside from the gas phase experiments 26,27 and the theoretical studies. [28][29][30][31][32] In these cases, the iron carbide nanoparticles exhibit superparamagnetism, i.e., they do not act as magnets at ambient temperature. However, sub-nanosized iron carbide particles have remained elusive to date.…”

“…S3a †) 40 as well as the theoretical studies. [28][29][30][31][32] It should be noted that atomic-resolution images that would project the clusters could not be obtained, because these samples exhibit ferromagnetism, even at room temperature (vide infra).…”

Evolution of Ferromagnetic and Antiferromagnetic States in Iron Nitride Clusters FenN and FenN2 (n = 1–10)

“…All computations were performed with the Gaussian 16 program using the all-electron spin-unrestricted density functional theory (DFT) with the BPW91 exchange-correlation functional , which incorporates the generalized gradient approximation (GGA). The BPW91 functional was found to be the best one among the tested DFT methods for the 3d-metal carbides − and oxides. , The reproduction of antiferromagnetic states in the Fe 8 and Fe 8 O 8 clusters was assessed using a variety of DFT methods such as BPW91, PW91, PBE, revTPSS, and M06L, and the BPW91 was found to be the most reliable among these methods in reproducing the geometrical structures and spin states. The 6-311+G* basis set of triple-ζ quality was used for both the Fe and the N atoms since it was found previously that the BPW91/6-311+G* method is capable of accurately reproducing experimental electron affinities in the Fe n O and CrC n series. , Experimental data for iron nitrides are scarce.…”