Density functional study on cage and noncage (Fe2O3)n clusters

Cationic iron-oxide clusters of several sizes and stoichiometries have been synthesized and studied isolated in the gas phase. Vibrational spectra of the clusters have been measured using resonant IR- With the continuous trend of increasing the density of electronic devices, novel concepts are needed to answer the increasing technical problems. Many of these concepts require the creation of dedicated nanosized building blocks with well understood and a priori designed properties. For application in quantum computing and storage, for example, chemically synthesized magnetic molecules were suggested as possible units. 1 In such a "bottom-up" approach, magnetic clusters represent the smallest chunks of matter where condensed matter properties start to appear, magnetic order, in particular. However, these properties are still drastically different from those of the bulk matter, making the clusters a new object of physical research. Such atomic clusters may be as small as containing only tens of atoms. 2 They allow a large freedom in manipulation through varying their composition and size, adding one atom at a time. 3 From various materials, transition-metal oxides represent the widest variety of phenomena, from ferroelectricity and magnetism to superconductivity, often combined. In cluster form, many unusual phenomena have been predicted. [4][5][6][7][8] The knowledge of their detailed magnetic, electronic, and ionic structure is essential for various applications, such as the formation of novel materials or design of next generation devices, to fundamental issues as the functioning of quantum and thermodynamics laws in ͑sub-͒ nanoscale systems.To explore the intrinsic properties of nanoparticles free of external perturbations, experiments are best performed in the gas phase. However, the experimental data on the properties of gas-phase transition-metal oxide clusters are still scarce. A preferred method to obtain information on structure and bonding is vibrational spectroscopy. Unfortunately, in most cases, isolated clusters can only be studied in molecular beams or ion traps 9 and the low particle density rules out direct absorption measurements. Furthermore, clusters are often produced in broad size distributions, making size selectivity essential. To overcome such problems, mass selected clusters can be embedded and accumulated in rare gas matrices. 10,11 In those experiments, interactions with the rare gas matrix may induce shifts of the absorption lines, and additionally, it cannot be excluded that structural changes during the deposition occur. Intense tunable infrared sources such as free-electron lasers allow different approaches. Thus, titanium 12 and zirconium 13 oxides were investigated with the help of infrared resonance enhanced multiple-photon ionization spectroscopy. Infrared photodissociation spectroscopy helped to determine the structure of oxide clusters of vanadium, 14 niobium and tantalum 15,16 as well as binary vanadium-titanium oxide clusters. 17 However, the possible existence of magnetic ord...

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“…21. Ferrimagnetic arrangement in our case though, explains the slight deviation from a tetrahedral structure leading to C 3v symmetry.…”

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confidence: 84%

Ferrimagnetic cagelikeFe4O6cluster: Structure determination from infrared dissociation spectroscopy

et al. 2010

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“…4,6,9,10,[13][14][15][16][17][20][21][22][23][24]26 The number of works in which Fe m O n clusters were studied with methods beyond DFT is very limited and restricted to very small cluster sizes. For FeO + its reactivity towards H 2 was studied on a wave-function-based CASPT2D level.…”

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confidence: 99%

“…[15][16][17][18][19] However, also the geometry and electronic structure of other cluster sizes have been studied theoretically. 15,[20][21][22][23][24][25] The prediction of geometric structures requires a systematic search of the potential energy surface to find the global minimum.…”

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confidence: 99%

Geometric, electronic, and magnetic structure ofFexOy+clusters

Logemann¹,

Wijs²,

Katsnelson³

et al. 2015

Phys. Rev. B

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Correlation between geometry, electronic structure and magnetism of solids is both intriguing and elusive. This is particularly strongly manifested in small clusters, where a vast number of unusual structures appear. Here, we employ density functional theory in combination with a genetic search algorithm, GGA+U and a hybrid functional to determine the structure of gas phase Fe In nano technology there is an ever increasing demand for increasing the density of electronic and magnetic devices. This continuous downscaling trend drives the interest to electronic and magnetic structures at the atomic scale. In essence, two things are required: first, novel materials and building blocks with exotic physical properties. Second, a fundamental knowledge of the physical mechanism of magnetism at the sub-nanometer scale.Atomic clusters, having highly non-monotonous behavior as a function of size, are a promising model system to study the fundamentals of magnetism at the nanoscale and below. Such clusters consist of only tens of atoms. Quantum mechanics starts to play an essential role at this small scale, adding extra degrees of freedom. Since these clusters are studied in high vacuum, they are completely isolated from their environment.To use these clusters as a model system, as a starting point, a detailed understanding of the relation between their geometry and electronic structure is required.Even in the bulk, iron oxide has a wide variety of chemical compositions and phases with many interesting phenomena, such as the Verwey transition in magnetite. 1,2Experiments performed on small gas phase Fe x O y clusters beyond the two-atom case are scarce. The structure of one and two Fe atoms with oxygen has been studied in an argon matrix using infrared spectra.3,4 The corresponding vibration frequencies have been identified using density functional theory (DFT).Iron-oxide nanoparticles have been investigated for their potential use as catalyst in chemical reactions.5 Furthermore, since the iron-oxygen interaction has a fundamental role in many chemical and biological processes, there have been quite some studies, both experimental and theoretical, of the chemical properties of Fe x O y clusters. 6-12The possible coexistence of two structural isomers for stoichiometric iron-oxide clusters in the size range n ≥ 5 was experimentally measured using isomer separation by ion mobility mass spectroscopy for Fe n O n and Fe n O n+1 (n = 2-9).13 Furthermore, the formation of Fe x O y clusters has been studied in the size range (x = 1-52). 14The number of theoretical studies is, however, manifold. The magic cluster Fe 13 O 8 was extensively studied and identified as a cluster with C 1 but close to D 4h point group symmetry.15-19 However, also the geometry and electronic structure of other cluster sizes have been studied theoretically.15,20-25 The prediction of geometric structures requires a systematic search of the potential energy surface to find the global minimum.The majority of theoretical studies were performed using DFT. 4,6,9,1...

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“…We began our extensive search for the global minima on the potential energy surfaces with the geometrical structures generated for Ti 8 O 12 using the global search as well as the structures we previously generated for Fe 8 O 12 and the structures from other work When searching for the energetically preferred distributions of local spin magnetic moments in antiferromagnetic (AFM) singlet states of M 8 O 12 , we used the electronic density distributions obtained for the AFM states of other clusters as the guess. In addition, we also used the fragment method of the G09 program for generating various distributions of the total local spin magnetic moments.…”

Section: Details Of Computationsmentioning

confidence: 99%

Hydrogenation of 3d‐metal oxide clusters: Effects on the structure and magnetic properties

et al. 2018

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The geometrical structures and properties of the M8O12, M8O12H8, and M8O12H12 clusters are explored using density functional theory with the generalized gradient approximation for all 3d‐metals M from Sc to Zn. It is found that the geometries and total spin magnetic moments of the clusters depended strongly on the 3d‐atom type and the hydrogenation extent. More than the half of all of the 30 clusters had singlet lowest total energy states, which could be described as either nonmagnetic or antiferromagnetic. Hydrogenation increases the total spin magnetic moments of the M8O12H12 clusters when MMnNi, which become larger by four Bohr magneton than those of the corresponding unary clusters M8. Hydrogenation substantially affects such properties as polarizability, forbidden band gaps, and dipole moments. Collective superexchange where the local total spin magnetic moments of two atom squads are coupled antiparallel was observed in antiferromagnetic singlet states of Fe8O12H8 and Co8O12H8, whereas the lowest total energy states of their neighbors Mn8O12H8 and Ni8O12H8 are ferrimagnetic and ferromagnetic, respectively. Hydrogenation leads to a decrease in the average binding energy per atom when moving across the 3d‐metal atom series. © 2018 Wiley Periodicals, Inc.

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Density functional study on cage and noncage (Fe2O3)n clusters

Cited by 50 publications

References 67 publications

Ferrimagnetic cagelikeFe4O6cluster: Structure determination from infrared dissociation spectroscopy

Ferrimagnetic cagelikeFe4O6cluster: Structure determination from infrared dissociation spectroscopy

Geometric, electronic, and magnetic structure ofFexOy+clusters

Hydrogenation of 3d‐metal oxide clusters: Effects on the structure and magnetic properties

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