Electronic and magnetic properties of Fe2Sin (1 ≤ n ≤ 12)+/0/− clusters (original) (raw)
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Fe encapsulation by silicon clusters: Ab initio electronic structure calculations
Physical Review B, 2003
Ab initio electronic structure calculations based on density functional theory are performed for Si n Fe clusters to determine stable structures. Our results show that these clusters can form the building block for Feencapsulated Si-nanotubes. The Si 10 Fe and Si 12 Fe clusters are found to be very stable, exhibiting large charge transfer, and can lead to Si-based nanotubes of the types Si 5n Fe nϪ1 and Si 6n Fe nϪ1 , respectively. The effect of Si encapsulation on the magnetic properties of the Fe atom is also investigated.
High Magnetic Moments in Manganese-Doped Silicon Clusters
Chemistry - A European Journal, 2012
We report on the structural, electronic, and magnetic properties of manganese-doped silicon clusters cations, Si n Mn + with n = 6−10, 12−14 and 16, using mass spectrometry and infrared spectroscopy in combination with density functional theory computations. This combined experimental and theoretical study allows several structures to be identified. All the exohedral Si n Mn + (n = 6−10) clusters are found to be substitutive derivatives of the bare Si n+1 + cations, while the endohedral Si n Mn + (n = 12−14 and 16) clusters adopt fullerene-like structures. The hybrid B3P86 functional is shown to be appropriate in predicting the ground electronic states of the clusters and in reproducing their infrared spectra. The clusters turn out to have high magnetic moments localized on Mn. In particular the Mn atoms in the exohedral Si n Mn + (n = 6−10) clusters have local magnetic moments of 4 µ B or 6 µ B and can be considered as magnetic copies of the silicon atoms. Opposed to other 3d transition metal dopants, the local magnetic moment of the Mn atom is not completely quenched when encapsulated in a silicon cage.
Magnetic moment and local moment alignment in anionic and/or oxidized Fe clusters
2010
First principles studies on the ground state structure, binding energy, spin multiplicity, and the noncollinearity of local spin moments in Fe n and Fe n − clusters and their oxides, viz., Fe n O 2 and Fe n O 2 − have been carried out within a density functional formalism. The ground states of Fe n and Fe n − clusters have collinear spins with a magnetic moment of around 3.0 B per atom. The O 2 molecule is found to be dissociatively absorbed and its most significant effect on spin occurs in Fe 2 , where Fe 2 O 2 and Fe 2 O 2 − show antiferromagnetic and noncollinear spin arrangements, respectively. The calculated adiabatic electron affinity and the vertical transitions from the anion to the neutral species are found to be in good agreement with the available negative ion photodetachment spectra, providing support to the calculated ground states including the noncollinear ones.
Cohesive, structural, and electronic properties of Fe-Si compounds
Physical Review B
Phase stability, structural, and electronic properties of iron silicides in the Fe 3 Si, FeSi, and FeSi 2 compositions are investigated by first-principle density-functional calculations based on ultrasoft pseudopotentials and all-electron methods. Structural stabilization versus spin-polarization effects are discussed at the Fe 3 Si composition, while for ⑀-FeSi and -FeSi 2 we investigate their structural properties and the corresponding semiconducting band properties. All the computed results are analyzed and compared to available experimental data. The stability of the bulk phases, the lattice parameters, the cohesive energies and magnetic properties are found to be in good agreement with experiment when using the generalized gradient approximations for the exchange-correlation functional. Density-functional calculations are unable to account for the small bulk modulus of ⑀-FeSi despite that the computed lattice constant and internal atomic positions coincide with the experimental results. Both full-potential and ultrasoft-pseudopotential methods confirm for -FeSi 2 the indirect nature of the fundamental gap, which is attributed to a transition between Y to 0.6ϫ⌳ being 30% smaller than the experimental gap. Ultrasoft pseudopotential calculations of Fe-Si magnetic phases and of various nonequilibrium metallic phases at the FeSi and FeSi 2 composition are presented. These calculations provide ab initio information concerning the stabilization of metallic pseudomorphic phases via high pressures or epitaxy. ͓S0163-1829͑99͒05419-3͔
Semiempirical study of electronic and bonding properties of iron silicide clusters
Theoretica chimica acta, 1990
The electronic structure of cobalt silicide clusters Co7Si7 and Si7C07 was studied in comparison to that of Co19 and Si17 clusters under the scope of the MINDOiSR method. Clusters Co7Si7 and Si7C07 represent the environment of a cobalt atom and that of a silicon atom in the cobalt monosilicide bulk, respectively. It is found that the Co-Si bond is essentially sp in character with an indirect participation (by electrostatic interaction) of the cobalt d orbitals. Our calculations show a charge transfer from silicon to the d orbitals of cobalt via sp-sp interaction with an internal sp-d hybridization. The theoretical density of states for cobalt silicide clusters are reported and compared with experimental results of surface spectroscopies. 0 1992 by John Wiley & Sons, Inc.
Zeitschrift für Naturforschung B, 1987
Hexanuclear Fe/Se/SR Complexes, Synthesis, X-Ray, Magnetic and Electrochemical Properties The compounds (PhCH 2 NEt 3) 4 [Fe 6 Se 9 (SMe) 2 ] (1) and (Et 4 N) 4 [Fe 6 Se 9 (SCH 2 Ph) 2 ] (2) have been isolated in good yields from Fe(SR) 3 (R = Me, CH 2 Ph)/"Na 2 Se 2 " reaction mixtures in methanol/N,N-dimethylformamide after addition of the appropriate tetraalkylammonium chlorides. 1 is monoclinic, space group P2]/c, Z = 4, with a = 18.697(14), b-22.606(16), c = 15.989(11) Ä, and/3 = 94.15(6)° at 140 K. Its structure has been refined to R (R w)-0.092 (0.075). The [Fe 6 Se 9 (SMe) 2 ] 4_ anion contains six coplanar iron atoms which are present in distorted tetrahedral Se 4 and Se 3 (SMe) ligand surroundings. The Se atoms are n, and fi 4 bridging. The four central Fe atoms and the Se atoms constitute a Fe 4 Se 9 group that is structurally related to 4[Fe 2 Se 3 ] 2_ double tetrahedral chains and 2 [FeSe] layers. The Fe atoms in the [Fe 6 Se 9 (SMe) 2 ] 4~ cluster are antiferromagnetically coupled. 1 has a room-temperature magnetic moment of 1.22 ,M B /Fe. Cyclic voltammograms, and electronic, infrared, and proton resonance spectra of 1 and 2 have been measured.
Inorganic Chemistry, 2005
Sulfur K-edge X-ray absorption spectroscopy of a hydrogen-bonded elongated [Fe 4 S 4 ] 2+ cube is reported. The data show that this synthetic cube is less covalent than a normal compressed cube with no hydrogen bonding. DFT calculations reveal that the observed difference in electronic structure has significant contributions from both the cluster distortion and from hydrogen bonding. The elongated and compressed Fe 4 S 4 structures are found to have different spin topologies (i.e., orientation of the delocalized Fe 2 S 2 subclusters which are antiferromagnetically coupled to each other). It is suggested that the H-bonding interaction with the counterion does not contribute to the cluster elongation. A magneto-structural correlation is developed for the Fe 4 S 4 cube that is used to identify the redoxactive Fe 2 S 2 subclusters in active sites of HiPIP and ferredoxin proteins involving these clusters.
Magnetic properties of dodecanuclear mixed valence iron clusters
Inorganica Chimica Acta, 1996
Slow addition of dioxygen to a basic methanol solution of iron(II) chloride afforded the mixed valent polyiron oxo cluster [Fel2(O)2(O2CCH2CI)5.3CIo. 7 (CH30)Is(CH3OH)4] (1). The structure of 1 was determined in a single crystal X-ray diffraction study; crystallographic data at 202 K: space group Pi, a = 10.606(2)/~, b = 12.173(2) ]~, c = 13.199(1)/~, cr = 100.48(1) °, ff = 96.63(1) °, ? = 91.43(1) °, V= 1662.5(4)~3, Z= 1, Mr= 1907.3, Peale = 1.91 g cm -3. For 3499 unique observed reflections with F 2 > 3or(F2), R = 0.060, R w = 0.063. The core of the cluster contains a face-centered cubic array of oxygen atoms with eight iron(II) ions and four iron(Ill) ions occupying oetahedral sites. Two/~6-oxo ligands link 10 of the 12 iron atoms. The mixed valent nature of this air-sensitive compound was established by analyzing the Fe-O distances, by charge considerations, and by electronic and M6ssbauer spectroscopy. Three iron subsites are resolvable in the M6ssbauer spectrum, corresponding to localized Fe(III) and Fe(II) ions and consistent with the crystallographic data. The magnetic properties of 1 were satisfactorily reproduced by a simple model which assumes that exchange coupling interactions mediated by #2-methoxo ligands are responsible for the observed magnetic behavior in the temperature range 20-300 K, whereas at lower temperature the effects of the #3-methoxo,/~2-carboxylato and/~6-oxo ligands become more important. This behavior is reflected by the appearance of magnetic features in the M6ssbauer spectra with decreasing temperature. The magnetic properties of 1 may be understood as arising from two subclusters, a and b, for which the following two sets of parameters are proposed and discussed: (i) g(a)= 2.319(3), g(b)= 1.831(4), J= 15.9(1) cm -1 and (ii) g(a)= 2.23(3), g(b)= 2.1(1), J= 19(2) cm -1, where J is the exchange coupling constant through/~2-methoxo bridges within the a subcluster, and the spins of subeluster b remain largely uncoupled.
The Journal of Physical Chemistry A, 2014
The structures of neutral cobalt doped silicon clusters have been assigned by a combined experimental and theoretical study. Size-selective infrared spectra of neutral Si n Co (n = 10−12) clusters are measured using a tunable IR-UV two-color ionization scheme. The experimental infrared spectra are compared with calculated spectra of low energy structures predicted at the B3P86 level of theory. It is shown that the Si n Co (n = 10−12) clusters have endohedral caged structures, where the silicon frameworks prefer double-layered structures encapsulating the Co atom. Electronic structure analysis indicates that the clusters are stabilized by an ionic interaction between the Co dopant atom and the silicon cage due to the charge transfer from the silicon valence sp orbitals to the cobalt 3d orbitals. Strong hybridization between the Co dopant atom and silicon host quenches the local magnetic moment on the encapsulated Co atom.
Journal of the American Chemical Society, 1995
Based on self-assembly of the dissymmetrical mononuclear entity CuL(CH 3 OH) [H 2 L = (E)-N 1-(2-((2-aminocyclohexydiimino)(phenyl)methyl)-4-chlorophenyl)-N 2-(2-benzyl-4-chlorophenyl)oxalamide] with Mn(II), two trinuclear complexes were prepared. They are of the formula [(LCuN 3) 2 Mn(CH 3 OH) 2 ] AE 2CH 3 OH AE 2H 2 O (1) and [(LCuSCN) 2 Mn(H 2 O) 2 ] AE 4CH 3 OH (2). Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = À14.40 cm À1 for 1 and J = À15.48 cm À1 for 2. Hydrogen bonds help complex 1 to produce a novel S type one-dimensional chain-like supramolecular structure. In complex 2, ClÁ Á ÁCl interaction also results in the formation of a one-dimensional structure.