Abstract
The mixed valence iron silicate ilvaite, CaFe 2+2 Fe3+Si2O8(OH), displays electron delocalization associated with Fe2+→Fe3+ charge transfer as observed by Mössbauer spectroscopy. Previous studies report the observation of an ‘electron hopping phenomenon’ with resolution of discrete valence states below 320 K. Mössbauer spectra of a suite of naturally occurring ilvaites were recorded over a temperature range, 80 K to 575 K. Five quadrupole doublets were resolved by computer fitting and assigned to Fe2+(A), Fe2+(B), Fe3+(A), and Fe2+(A)→Fe3+(A)‖c and ⊥c. Contrary to prior work, doublets associated with electron delocalization are resolved at 80 K and preclude the use of a Verwey-type order-disorder model. We propose a thermal activation model and discuss its criteria from molecular orbital and mineralogical viewpoints.
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References
Ballhausen, C.J., Gray, H.B.: Molecular Orbital Theory. New York: Benjamin 1964
Bancroft, G.M., Burns, R.G., Maddock, A.G.: Applications of the Mössbauer effect to silicate mineralogy: I Iron silicates of known crystal structure. Geochim. Cosmochim. Acta 31, 2219–2246 (1967)
Bancroft, G.M., Burns, R.G., Stone, A.J.: Applications of the Mössbauer effect to silicate mineralogy: II Iron silicates of unknown and complex crystal structures. Geochim. Cosmochim. Acta 32, 547–559 (1968)
Belov, N.V., Mokeeva, V.I.: The crystal structure of ilvaite. Trudy Inst. Krist. Akad. Nauk. SSSR 9, 89–102 (1954)
Beran, A., Bittner, H.: Untersuchungen zur Kristallchemie des Ilvaits. Tschermaks Mineral. Petrog. Mitt. 21, 11–29 (1974)
Borshagovskii, B.V., Marfunin, A.S., Mkrtchyan, A.R., Nagyaryan, G.N., Stukan, R.A.: Mössbauer study of isomorphous substitution in ilvaite. Phys. Status Solidi (B) 43, 479–482 (1971)
Burns, R.G., Parkin, K.M., Loeffler, B.M., Leung, I.S., Abu-Eid, R.M.: Further characterization of spectral features attributable to titanium on the moon. Proc. 7th Lunar Sci. Conf. 2561-2578 (1976)
Cullen, J.R., Callen, E.: Band theory of multiple ordering and the metal-semiconductor transition in magnetite. Phys. Rev. Lett. 26, (5) 236–238 (1971)
Day, P.: Mixed valence chemistry and metal chain compounds. In: Low Dimensional Cooperative Phenomena, Keller, H.J. (ed.) 1976
Evans, B.J.: Experimental studies of the electrical conductivity and phase transition in Fe3O4, Wolfe, H.C. (ed.). AIP Conf. Proc. on Magnetism and Magnetic Materials # 24, 73–78 (1975)
Gerard, A., Grandjean, F.: Observation by Mössbauer effect of an electron hopping process in ilvaite. Solid State Commun. 9, 1845–1849 (1971)
Ghose, S.: Crystal chemistry of iron. In: Handbook of Geochemistry, Vol. II/1, 26-A. Wedepohl, K.H. (ed.). Berlin, Heidelberg, New York: Springer 1969
Grandjean, F., Gerard, A.: Analysis by Mössbauer spectroscopy of the electronic hopping process in ilvaite. Solid State Commun. 16, 553–556 (1975)
Haga, N., Takeuchi, Y.: Neutron diffraction study of ilvaite. Z. Krist. 144, 161–174 (1976)
Heilmann, I.U., Olsen, N.B., Olsen, J.S.: Electron hopping and temperature dependent oxidation states of iron in ilvaite studied by Mössbauer effect. Phys. Scripta 15, 285–288 (1977)
Herzenberg, C.L., Riley, D.L.: Oxidation states and site symmetries of iron in ilvaite using Mössbauer spectrometry. Acta Cryst. A25, 389–391 (1969)
Huggins, F.E.: Mössbauer studies of iron minerals under pressures of up to 200 kbars. Ph.D. Thesis Massachusetts Institute of Technology (1975)
Kündig, W., Hargrove, R.S.: Electron hopping in magnetite. Solid State Commun. 7, 223–227 (1969)
Loeffler, B.M., Burns, R.G., Tossell, J.A.: Metal-metal charge transfer transitions: Interpretations of visible-region spectra of the moon and lunar materials. Proc. 6th Lunar Sci. Conf. 3, 2663–2676 (1975)
Lotgering, F.K., Diepen, A.M. van: Electron exchange between Fe2+ and Fe3+ ions on octahedral sites in spinels, studied by means of paramagnetic Mössbauer spectra and susceptibility measurements. J. Phys. Chem. Solids 38, 565–572 (1977)
Mayoh, B., Day, P.: Charge transfer in mixed valence solids. Part VII Perturbation calculations of valence delocalization in iron (II, III) cyanides and silicates. J. Chem. Soc. Dalton Trans. 846-852 (1974)
Nolet, D.A., Burns, R.G.: Temperature Dependent Fe2+ → Fe3+ electron delocalization in ilvaite. Geophys. Res. Lett. 5, (10) 821–824 (1978)
Osborne, M.D., Parkin, K.M., Burns, R.G.: Temperature-dependence of Fe-Ti spectra in the visible region: Implications to mapping Ti concentrations of hot planetary surfaces. Proc. 9th Lunar Sci. Conf. 2949–2960 (1978)
Paques-Ledent, M.T., Grandjean, F., Gerard, A.: Chemical formula of ilvaite: Infrared and Mössbauer data. Bull. Soc. R. Sci. Liege 46, (9–10) 337–342 (1977)
Ruby, S.L.: Why MISFIT when you already have x 2? In: Mössbauer Effect Methodology, Vol. 8, Gruverman, J. (ed.). New York: Plenum Press 1973
Sawatzky, G.A., Coey, J.M.D., Morrish, A.N.: Mössbauer study of electron hopping in the octahedral sites of Fe3O4. J. Appl. Phys. 40, (3), 1402–1403 (1969)
Schwartz, K.B., Nolet, D.A., Burns, R.G.: Mössbauer spectroscopy and crystal chemistry of natural Fe-Ti garnets. Am. Mineral. 64 (in press, 1979)
Smith, G., Strens, R.G.J.: Intervalence-transfer absorption in some silicate, oxide, and phosphate minerals. In: The Physics and Chemistry of Minerals and Rocks, Strens, R.G.J. (ed.). New York: J. Wiley & Sons 1976, pp. 583–612
Stone, A.J., Augard, H.J., Fenger, J.: MOSSPEC. Program for resolving Mössbauer spectra. Publ. Danish Atomic Energy Comm. RISO-M-1348 (1971)
Tossell, J.A., Gibbs, G.V.: Molecular orbital studies of geometries and spectra of minerals and inorganic compounds. Phys. Chem. Minerals 2, 21–57 (1977)
Vaughan, D.J., Tossell, J.A.: Major transition-metal oxide minerals: Their electronic structures and the interpretation of their mineralogical properties. Can. Mineral. 16, 159–168 (1978)
Verble, J.L.: Temperature-dependent light scattering studies of the Verwey transition and electronic disorder in magnetite. Phys. Rev. (B) 9, (12) 5236–5248 (1974)
Verwey, E.J., Haayman, P.W.: Electronic conductivity and transition point of magnetite (‘Fe3O4’). Physica 8, 979–987 (1941)
Warner, B.N., Shive, P.N., Allen, J.L., Terry, C.: A study of the hematite-ilmenite series by the Mössbauer effect. J. Geomag. Geoelectr. 24, 353–367 (1972)
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Nolet, D.A., Burns, R.G. Ilvaite: A study of temperature dependent electron delocalization by the mössbauer effect. Phys Chem Minerals 4, 221–234 (1979). https://doi.org/10.1007/BF00307946
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DOI: https://doi.org/10.1007/BF00307946