Fe-O Interactions Research Articles

Turning waste into Wealth: Collaborative enhancement of sucralose degradation and ilmenite aeration purification

Integrating sucralose degradation with the aeration purification of reduced ilmenite presents an untapped opportunity for enhancing aeration efficiency and promoting wastewater utilization. Herein, aeration experiments conducted at 80 °C with a 2 % sucralose concentration yielded an 18 % enhancement in aeration efficiency, a 21.5 % decrease in energy expenditure, and the sucralose content was reduced to 2.5 %. Density functional theory calculations and computational fluid dynamics confirm the formation of Fe-O interactions between sucralose and γ-FeOOH colloids, which produce flocculation, decrease slurry viscosity, and enhance oxygen transfer, thereby improving aeration efficiency. Furthermore, FeCl3, generated during aeration, catalyzes sucralose degradation. This study provides a theoretical foundation and practical experience for the synergistic application of wastewater and mineral processing.

Systematic Exploration of the Interactions between Pyrite and Coal from the View of Density Functional Theory

Coal is often adhered to by pyrite during slime flotation, causing an increase in the sulfur content of clean coal. In order to study the mechanism of pyrite adhesion to coal surfaces, different coal structural units were built and optimized, and the most stable adsorption model of them on pyrite surfaces was determined. The mechanism of pyrite particles adhering to the surface of coal slurries was explored with the method of DFT. The results showed that the interaction mechanism between pyrite surface and Ph-OH and Ph-O-CH3 was the result of a weak interaction between the H atom of Ph-OH and Ph-O-CH3 and the S atom of the pyrite surface. The interaction mechanism between the pyrite surface and Ph-COOH and Ph-CO-CH3 was both as a result of H-S interactions and weak Fe-O interactions. On the whole, there were weak interactions between pyrite particles and the coal slurry, and the pyrite particles can spontaneously adsorb on the surface of the coal slurry.

Enhanced waste Plastics-to-Power in situ conversion through iron oxide as pseudofuel in solid oxide fuel cells

Waste plastics-to-power conversion via fuel cells is very attractive for its potential to be efficient and eco-friendly. Here we report a solid oxide fuel cell (SOFC) operating directly on waste polyethylene terephthalate (PET) with significantly improved performance due to the modification of anode with iron oxide (Fe2O3) that functions as pseudofuel in its reduced form (FeO). The pseudofuel performance, namely the discharge capacity of FeO, was improved significantly by optimizing the structure of Fe2O3, and owing to the synergistic interaction of FeO with the anodic materials, i.e. silver and gadolinia doped ceria. A mechanism is proposed to reveal the synergistic effect of these materials in the discharge process. The maximum discharge capacity of 340 mAh/g for FeO was obtained, approaching 91 % of the theoretical value. Based on the optimized pseudofuel, the electrochemical performance of SOFCs directly fueled by waste PET was markedly enhanced: The peak power density of the cell increased from 115 to 320 mW cm−2, and the electric energy output of the PET fuel did from 0.0018 to 0.26 Wh/g (140-fold more). This work shows that SOFCs with Fe2O3 modified Ag-based anode offer a promising platform for direct conversion of plastic waste to power in an efficient and green manner.

Carbon monoxide and hydrogen reduction of metals from the B2O3 – CaO – FeO – PbО melts: thermodynamic modelling

A thermodynamic modelling procedure has been developed that enables to predict the results of metal reduction from oxide melt in bubbling units by building an almost-true-to-real-process model. The procedure involves determining an equilibrium for each introduced portion of gas while taking the concentrations of target metal oxides in every modelling cycle from the previous data. The resultant metal phases and gases are excluded from the following calculations. This approach helps make the models most true to real processes and analyze how complete the reactions are that take place in pyrometallurgical units. The authors use the above procedure to describe the processes of combined iron and lead reduction from the B2O3 – CaO – FeO – PbO melt by carbon monoxide and hydrogen. This paper includes a comparative analysis of how the temperature T and the amount of V СО or VН2 gas introduced can impact the reduction of lead and iron from an oxide melt. The B2O3/CaO ratio taken for the modelling purposes is equal to 3, which corresponds to eutectic composition. The initial concentration of components, wt. %: 58.5 В2О3; 19.5 СаО; 20.0 FeO; 2 PbО; the temperature range: 1273–1773 К. The calculations were carried out based on the disproportionation of FeO into Fe and Fe3O4. The interaction of FeO and Fe with PbO ensures a partial transition of lead in metallic state. Depending on the temperature, the degree of lead metallization can vary from 76.8 (at 1,273 К) to 19.4 % (at 1,773 К). As the temperature rises, the concentration of FeO and PbO in the melt tends to increase whereas that of Fe3O4 tends to decrease. The authors analyzed how the concentration of lead and iron oxides in the melt and their reduction degree changed depending on the amount of reducing agent introduced. In the case of lead and iron reduction, no difference in the resulting products was found when using hydrogen versus carbon monoxide as the reducing agent. At the same time, hydrogen reduction results in a more complete reaction compared with carbon monoxide reduction. Thus, a smaller amount of gas is required to achieve a close-to-100% reduction of lead: СО — 10÷13 dm3/kg, Н2 — 5.8÷10.1 dm3/kg. Higher temperatures lead to the transition of some of the lead in gas phase. The obtained data indicate that one should account for the disproportionation of FeO into Fe3O4 and Fe when analyzing the interaction between the reducing agent (carbon monoxide or hydrogen) and the B2O3 – CaO – FeO – PbО oxide melt in the bubbled layer, which is associated with the changing composition of the melt.The work was conducted according to the State assignment of the Institute of Metallurgy of the RAS Ural branch (State registration of the theme No. 122020100404-2).

Characterization of the binding affinity between some anti-Parkinson agents and Mn2+, Fe3+ and Zn2+ metal ions: A DFT insight

In the current work, density functional theory calculations were carried out to evaluate the potential ability of apomorphine, dopamine, hinokitiol and deferiprone chelating agents to coordinate Mn2+, Fe3+ and Zn2+ metal ions with a 1:1 ratio in water solution. The binding energy values reveal that Zn2+/chelating agent complexes are more stable compared to Mn2+/chelating agent and Fe3+/chelating agent complexes. In order to evaluate the parameters that describe the affinity between the metal ions and chelating agents, the metal ion/chelating agent interactions were analyzed by CDA, NBO, QTAIM, FMO analyses. Interestingly, it was found that the FeO interactions in all complexes and MnO interactions in [Mn-DFP]+ complex are mainly electrostatic, whereas other interactions have a covalent character. Moreover, TD-DFT studies showed n → π* and π → π* transitions in the absorption spectra of the complexes.

Influence of the Fe-Si-O framework in crystal structure on the phase stability and electrochemical performance of Li2FeSiO4 cathode

Understanding the influence of crystal structures on properties is significant in the future optimization and design of Li-ion battery cathodes. By using the first-principles calculations, we perform a comprehensive investigation on the crystal structure, phase stability and electrochemistry of three new predicted Li2FeSiO4 polymorphs with 1D (One-Dimensional), 2D and 3D Fe-Si-O frameworks, i.e. Cmcm, Pmna and P212121, respectively. Three Li2FeSiO4 polymorphs studied here are all mechanically, dynamically and thermodynamically stable. The Pmna is the favored phase at lower temperature and higher pressure, while P212121 and Cmcm phases could be obtain by quenching of fast cooling from higher temperature. Three Li2FeSiO4 polymorphs with different Fe-Si-O frameworks possess similar redox reactions mechanism. However, the oxidation potentials of Fe2+/Fe3+ reaction depends on the Fe-Si-O frameworks, which can be attributed to different FeO interactions. In addition, the phase transformation due to Li/Fe antisite could occur in Cmcm and Pmna polymorphs upon delithiated from Li2FeSiO4 to LiFeSiO4. While, P212121 polymorph with 3D Fe-Si-O framework shows better structural stability upon cycling. Finally, the Li diffusion mechanism in these three predicted polymorphs is also studied.

Local structure analysis of BO6 (B = Fe, Cu) octahedron correlated with the magnetic properties of Cu-doped Ba0.5Sr0.5FeO3–δ

Perovskite-based Ba0.5Sr0.5Fe1–xCuxO3–δ (BSFCO-x, x = 0–0.2) was synthesized by sol–gel self-combustion method. The crystallinity was evaluated through X-ray diffraction, besides further local structure analysis, using X-ray absorption spectroscopy (XAS) showed a cubic symmetry for x = 0.05; 0.10, which was tetragonal at higher values, x = 0.15; 0.20. XAS analysis predicted the oxidation state (OS) of Cu to be a mixture of 3+ and 2+, while Fe includes 3+ and 4+. Conversely, the OS of Fe and Cu in the octahedron site influence the number of an unpair electron that determine the magnetic properties of perovskite. In addition, the magnetization for Ba0.5Sr0.5FeO3–δ is 0.172 emu g−1, originating from the ferromagnetic ordering Fe3+(t 2g 3 e g 2 )–O (2p)–Fe4+(t 2g 3 e g 1 ) interaction. This effect increase, due to the presence of oxygen vacancy in BSFCO-0.05, which weakens the d–p interaction of Fe-O, while the generation of higher Cu doping to increase the amount of Fe4+ leads to a decline in Cu3+. Therefore, Cu doping is confirmed to play a role in the paramagnetic–ferromagnetic transition.

An efficient way to model complex magnetite: Assessment of SCC-DFTB against DFT.

Magnetite has attracted increasing attention in recent years due to its promising and diverse applications in biomedicine. Theoretical modelling can play an important role in understanding magnetite-based nanomaterials at the atomic scale for a deeper insight into the experimental observations. However, calculations based on density functional theory (DFT) are too costly for realistically large models of magnetite nanoparticles. Classical force field methods are very fast but lack of precision and of the description of electronic effects. Therefore, a cheap and efficient quantum mechanical simulation method with comparable accuracy to DFT is highly desired. Here, a less computationally demanding DFT-based method, i.e., self-consistent charge density functional tight-binding (SCC-DFTB), is adopted to investigate magnetite bulk and low-index (001) surfaces with newly proposed parameters for Fe-O interactions. We report that SCC-DFTB with on-site Coulomb correction provides results in quantitatively comparable agreement with those obtained by DFT + U and hybrid functional methods. Therefore, SCC-DFTB is valued as an efficient and reliable method for the description magnetite. This assessment will promote SCC-DFTB computational studies on magnetite-based nanostructures that attract increasing attention for medical applications.

Catalytic N2O decomposition and reduction by NH3 over Fe/Beta and Fe/SSZ-13 catalysts

Fe/zeolites are important N2O abatement catalysts, efficient in direct N2O decomposition and (selective) catalytic N2O reduction. In this study, Fe/Beta and Fe/SSZ-13 materials were synthesized via solution ion-exchange and used to catalyze these two reactions. The nature of the Fe species was probed with UV–vis, Mössbauer and EPR spectroscopies and H2-TPR. These characterizations collectively indicate that primarily isolated and dinuclear Fe sites are present in Fe/SSZ-13, whereas Fe/Beta contains higher concentrations of oligomeric FexOy species. H2-TPR results suggest that Fe-O interactions are weaker in Fe/SSZ-13, as evidenced by the lower reduction temperatures by H2 and higher extents of autoreduction during high-temperature pretreatments in inert gas. Kinetic measurements show that Fe/SSZ-13 has higher normalized reaction rates in catalytic N2O decomposition, thus demonstrating a positive correlation between reaction rate and Fe-O binding, consistent with O2 desorption being rate-limiting for this reaction. However, Fe/Beta was found to display higher reaction rates in catalyzing N2O reduction by NH3. This latter result indicates that larger active ensembles (i.e., oligomers) are responsible for this reaction, consistent with the fact that both N2O and NH3 need to be activated in this case.

The Oligomeric Form of the Escherichia coli Dps Protein Depends on the Availability of Iron Ions

The Dps protein of Escherichia coli, which combines ferroxidase activity and the ability to bind DNA, is effectively used by bacteria to protect their genomes from damage. Both activities depend on the integrity of this multi-subunit protein, which has an inner cavity for iron oxides; however, the diversity of its oligomeric forms has only been studied fragmentarily. Here, we show that iron ions stabilize the dodecameric form of Dps. This was found by electrophoretic fractionation and size exclusion chromatography, which revealed several oligomers in highly purified protein samples and demonstrated their conversion to dodecamers in the presence of 1 mM Mohr’s salt. The transmission electron microscopy data contradicted the assumption that the stabilizing effect is given by the optimal core size formed in the inner cavity of Dps. The charge state of iron ions was evaluated using Mössbauer spectroscopy, which showed the presence of Fe3O4, rather than the expected Fe2O3, in the sample. Assuming that Fe2+ can form additional inter-subunit contacts, we modeled the interaction of FeO and Fe2O3 with Dps, but the binding sites with putative functionality were predicted only for Fe2O3. The question of how the dodecameric form can be stabilized by ferric oxides is discussed.

Structure investigation of nano-FeO(OH) modified clinoptilolite tuff for antimony removal

Biomimetic sol-gel synthesis was used to prepare new FeO(OH) zeolite (clinoptilolite tuff) adsorbent effective for antimony removal. The product was compared with other on the market accessible natural or commercial adsorption materials like granulated ferric hydroxide GEH, powder of zero valent iron (ZVI)- nanofer and the new synthesized oxi(hydr)oxide FeO(OH) and characterized by XRD, XPS, Raman, FT IR, TG, DTA, DTG, TEM and SEM techniques. Based upon the SEM analysis, the oxidized nanofer sample revealed the existence of hematite and goethite and morphology of FeO(OH) dopant confirmed the presence of ferrihydrite, in less extent also magnetite and hematite. Recorded exothermic maxima on DTA curves for powdered FeO(OH) zeolite at 460 °C and for pure component FeO(OH) at 560 °C indicated an 100 °C shifted exothermic effect, which characterized strong chemical interaction of FeO(OH) with zeolite structure. Based upon the XPS analyses, also the difference between Fe species in the raw and FeO(OH) doped zeolite was found in increasing Si/Al ratio, however only at the surface below app. 5 nm, measured as 3.94 for raw and 5.38 for sample treated with alkalic solution. The plotting of adsorption isotherms in the system studied clearly showed the increasing uptake capacity of the adsorbents towards antimony with the increased S(BET) data (GEH ˃FeO(OH)˃FeO(OH) zeolite˃nanofer).

Theoretical Investigation of the Oxidation of Propane by FeO+

We report herein a comprehensive theoretical study of the oxidation of propane by FeO(+) on both the sextet and quartet potential energy surfaces (PESs) using density functional theory. The geometries and energies of all the stationary points involved are located. Interaction of FeO(+) with propane could account for four types of encounters (i.e., alpha,beta,gamma-, 2alpha,beta-, 3alpha-eta(3), and 2alpha,2gamma-eta(4)) complexes. Various mechanisms leading to the loss of CH(3), H(2)O, C(3)H(7)OH (H(2)O + C(3)H(6)), and C(3)H(6) are analyzed in terms of the topology of the PES. The reaction of FeO(+) with propane involves initial C-H activation, while initial C-C activation is indeed unlikely to be important. The loss of CH(3) takes place adiabatically on the sextet PES via the simple C(alpha)-to-O H shift from eta(4)-OFe(+)(C(3)H(8)) followed by CH(3) shift. The C(3)H(7)OH elimination proceeds via direct C(alpha)-to-O H shift followed by C-O coupling, while the loss of H(2)O, C(3)H(6), and (H(2)O + C(3)H(6)) proceeds via the alpha,beta-H and beta,alpha-H abstraction mechanisms from all the eta(3) complexes. The most favorable channel is the alpha,beta-H abstraction mechanism for the H(2)O loss because it not only is energetically and dynamically favorable but also has a high crossing probability between the sextet and quartet PESs. The computational results are in concert with the available experimental information and add new insight into the details of the individual elementary steps.

Experimental Bond Critical Point and Local Energy Density Properties Determined for Mn−O, Fe−O, and Co−O Bonded Interactions for Tephroite, Mn2SiO4, Fayalite, Fe2SiO4, and Co2SiO4Olivine and Selected Organic Metal Complexes: Comparison with Properties Calculated for Non-Transition and Transition Metal M−O Bonded Interactions for Silicates and Oxides

Bond critical point (bcp) and local energy density properties for the electron density (ED) distributions, calculated with first-principle quantum mechanical methods for divalent transition metal Mn-, Co-, and Fe-containing silicates and oxides are compared with experimental model ED properties for tephroite, Mn 2SiO 4, fayalite, Fe 2SiO 4, and Co 2SiO 4 olivine, each determined with high-energy synchrotron single-crystal X-ray diffraction data. Trends between the experimental bond lengths, R(M-O), (M = Mn, Fe, Co), and the calculated bcp properties are comparable with those observed for non-transition M-O bonded interactions. The bcp properties, local total energy density, H( r c), and bond length trends determined for the Mn-O, Co-O, and Fe-O interactions are also comparable. A comparison is also made with model experimental bcp properties determined for several Mn-O, Fe-O, and Co-O bonded interactions for selected organometallic complexes and several oxides. Despite the complexities of the structures of the organometallic complexes, the agreement between the calculated and model experimental bcp properties is fair to good in several cases. The G( r c)/rho( r c) versus R(M-O) trends established for non-transition metal M-O bonded interactions hold for the transition metal M-O bonded interactions with G( r c)/rho( r c) increasing in value as H( r c) becomes progressively more negative in value, indicating an increasing shared character of the interaction as G( r c)/rho( r c) increases in value. As observed for the non-transition metal M-O bonded interactions, the Laplacian, nabla (2)rho( r c), increases in value as rho( r c) increases and as H( r c) decreases and becomes progressive more negative in value. The Mn-O, Fe-O, and Co-O bonded interactions are indicated to be of intermediate character with a substantial component of closed-shell character compared with Fe-S and Ni-S bonded interactions, which show greater shared character based on the | V( r c)|/ G( r c) bond character indicator. The atomic charges conferred on the transition metal atoms for the three olivines decrease with increasing atomic number from Mn to Fe to Co as the average M-O bond lengths decrease from 2.219 to 2.168 to 2.128 A, respectively.

EXAFS Study on the Reactions between Iron and Fulvic Acid in Acid Aqueous Solutions

Iron(III) competes with trace metals for binding sites on organic ligands. We used X-ray absorption fine structure (EXAFS) spectroscopy to determine the binding mode and oxidation state of iron in solutions initially containing only iron(III) and fulvic acid at pHs 2 and 4. EXAFS spectra were recorded at different times after sample preparation. Iron was octahedrally configured with inner-sphere Fe-O interactions at 1.98-2.10 A, depending on the oxidation state of iron. Iron(III) formed complexes with fulvic acid within 15 min. Iron(III) was reduced to iron(II) with time at pH 2, whereas no significant reduction occurred at pH 4. No signs of dimeric/trimeric hydrolysis products were found in any of the solution samples (<0.45 microm). However, the isolated precipitate of the pH 2 sample (>0.45 microm) showed Fe...Fe distances, indicating the presence of tightly packed iron(III) trimers and/or clusters of corner-sharing octahedra. It is suggested that the binding mode of iron(III) to fulvic acid at low pH may be phase-dependent: in solution mononuclear complexes predominate, whereas in the solid phase hydrolyzed polynuclear iron(III) complexes form, even at very low pH values. The observed pH dependence of iron(III) reduction was consistent with expected results based on thermodynamic calculations for model ligands.

Interaction of FeO+ cation with benzene, aniline, and 3‐methylaniline: DFT study of oxygen insertion mechanism

AbstractThe reaction pathways and energetics for oxygen insertion into CH bond in benzene, aniline, and 3‐methylaniline by FeO+ in the gas phase were investigated by means of the DFT methodology with the B3LYP exchange‐correlation functional and 6‐311G** basis set. The main aim of this work was to elucidate the influence of substituents in phenyl ring on stationary points along the energy profile on sextet and quartet surfaces for the reaction of FeO+ with substituted benzenes. The studies show that the amino and methyl groups change the energetics of oxygen insertion by lowering the energy profile along the reaction pathway. The substituents studied in this work facilitate the insertion of oxygen into the aromatic CH bond by stabilizing the intermediate sigma complex (σ‐complex), the amino group being by far more effective. On the other hand, both functional groups increase the activation energy of the rate‐determining step in the gas phase, so that they have unfavorable influence on the kinetics. The comparison of the energy diagrams for the sextet and quartet spin states indicates the dominance of the low‐spin reactivity in oxygen insertion into aromatic CH bond. Aniline and 3‐methylaniline oxidation occurs via electrophilic addition while the conversion of benzene to phenol by FeO+ is mediated by a σ‐complex with mixed radical and cationic character. Present results are also discussed in the context of oxyferryl group reactivity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Effect of Novel Supporter on Catalytic Combustion of Methane

A new catalyst support, Ce-Mg-O, was prepared in a novel way macromolecule surfactant modified method and was used as a catalyst support for low-temperature methane combustion. The results indicate that the new type of FeO x /Ce-Mg-O catalyst exhibits high activity in low-temperature methane combustion, such that the T 90 at which 90% conversion of methane occurs can be obtained at 560 °C. The structure of the catalyst and the effect of the supporter on catalytic activity were characterized by transmission electronic microscopy (TEM), X-ray diffraction (XRD), and temperature-programmed reduction (TPR). The results indicate that the high catalytic activity of FeO x /Ce-Mg-O over methane combustion is strongly dependent on the particle size, typical crystal phase of the Ce-Mg-O, and the interaction of FeO x and Ce-Mg-O.

Crystal structure, magnetic properties, and Mössbauer studies ofLa0.6Sr0.4FeO3−δprepared by quenching in different atmospheres

Samples of ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{FeO}}_{3\ensuremath{-}\ensuremath{\delta}}$ compounds prepared by quenching in different gaseous environments were studied by x-ray diffraction, neutron diffraction, magnetization measurements, and M\ossbauer spectroscopy (MS). All materials are single phase and crystallize in the rhombohedral perovskite structure. Samples prepared in flowing air, ${\mathrm{N}}_{2},$ and ${\mathrm{O}}_{2}$ yielded oxygen vacancies ranging from 0% to 1%. The oxygen vacancy concentration increases from 6.8% to 9.6% as the ratio of ${\mathrm{C}\mathrm{O}/\mathrm{C}\mathrm{O}}_{2}$ changes from 10:90 to 90:10. The air-, ${\mathrm{N}}_{2}\ensuremath{-},$ and ${\mathrm{O}}_{2}$-quenched samples have a magnetic ordering temperature in the range of 300--325 K. The magnetic ordering temperature increases for all the samples subjected to the reducing ${\mathrm{C}\mathrm{O}/\mathrm{C}\mathrm{O}}_{2}$ atmosphere. The neutron data refinements and magnetization data indicate that the Fe sublattice of ${\mathrm{La}}_{0.6}{\mathrm{Sr}}_{0.4}{\mathrm{FeO}}_{3\ensuremath{-}\ensuremath{\delta}}$ has an antiferromagnetic structure below the magnetic ordering temperature. The Fe atoms possess a magnetic moment of $3.8{\ensuremath{\mu}}_{B}$ and a hyperfine field of 53 T in the ${\mathrm{C}\mathrm{O}/\mathrm{C}\mathrm{O}}_{2}$-quenched samples. It is found that the heat treatment in the ${\mathrm{C}\mathrm{O}/\mathrm{C}\mathrm{O}}_{2}$ atmosphere creates more oxygen vacancies, changes the Fe valence states, and increases the unit cell volume. In the meantime, the Fe-O-Fe bond angle increases. These dramatically affect the Fe-O-Fe superexchange coupling. The change of the Fe-O-Fe bond angle and the change of the Fe valence states in the ${\mathrm{C}\mathrm{O}/\mathrm{C}\mathrm{O}}_{2}$ heat treatment play a key role in the increase of the magnetic ordering temperatures and the magnetic moment. Therefore by creating oxygen vacancies or having excess oxygen, the exchange interaction of Fe-O and the valence state of Fe ions are affected, and lead to large changes in the magnetic properties, such as the magnetic ordering temperature, the magnetic moments, and the hyperfine interactions in the pervoskite structure.

Synchrotron X-ray study of the electron density in α-Al2O3

Structure factors for synthetic haematite, α-Fe 2 O 3 , have been measured for two small crystals using focused λ=0.7 A synchrotron radiation. The structure factors from the two data sets are consistent. Approximate symmetry in the concordant densities, related more closely to the Fe-Fe geometry than to the nearest-neighbour Fe-O interactions, is similar to that in the corundum α-Al 2 O 3 structure. Deformation density maxima are located at the midpoint of the Fe-Fe vector along the c axis, on a common face for O-octahedra, perpendicular to c. Maxima also occur at the midpoint of the Fe-Fe vector bisecting the edges of the O-octahedra. These results are in accordance with theoretical predictions for metal-metal bonding

Infrared Spectra of {Y3}[Mgy M 2-y](M 3-ySiy)O12 Garnets (M=Al3+, Fe 3+, Ga3+, y=0. 0 to 2. 0)

IR spectra in the region from 1200 to 200 cm-i of the garnet selid solutions 1{Ys}[MgvMa, ](MsntvSiy)Ois (M=AIS, FeS, GaS, y=O. O te 2, 0) have been studied systematically and strongly localized group vibration of isolated tetrahedren er octahedren was feund. The spectra assigried to stretching vibratiofi, y3, of tetrahedra, AIOt, FeOa, and GaO4, splitted intothree bands in y=O, O co ositi n Qf each s 1id sdut n 3 bands f A10'degenerqted into two bands at y l O.5, but those of FeOi or GaO' degenerated into oRe band at y 41.5 (Tables 1, 2 and 3, Fig.1, 2 and 3). ys bands shifted toward lower frequency with increasing y value for AIO' (substituting octahedral AIS by Mgg) but not remarkably for FeO4 or GaO4 (substituting octahedral Feg or GaS by Mg) (Fig.4). From these results and the report of McDevitt, it is concluded that the frequency of ys vibration of tetrahedron is affected by the ionic radius, that is, ionic field strength of neighbeuring dodecahedral and octahedral cations. The similar frequency shifts were also evident in the case of ys bands of SiO' (Fig.5). The difference of degeneration tendeney of v3 bands between AIO' and FeOt or GaOd suggests that the bonding character of FeO, or GaOA differs from that of AIO': the interaction of FeO' or GaO' with the garnet lattice seems to be small comparing with that ef AIO'. The bands assigned to stretching vibration of oetahedron were 520, 474, and 438 cmmi for AIO6, 382 and 362 cm-i for FeOs, 466, 400, and 342 cm-i for GaOs, and 400. v350 cm'i for MgO6, respectively.