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  • 1
    Electronic Resource
    Electronic Resource
    Infrared spectroscopy of natural, synthetic, and oxygen-18-substituted .alpha.-tridymite: structural implications (1992)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 10213-10218 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100204a023
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  • 2
    Electronic Resource
    Electronic Resource
    Compressibility and high-pressure phase transition of a metalloporphyrin: (5,10,15,20-tetraphenyl-12H,23H-porphinato)cobalt(II) (1987)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 91 (1987), S. 5042-5045 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100303a031
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  • 3
    Electronic Resource
    Electronic Resource
    Single-crystal absorption and reflection infrared spectroscopy of forsterite and fayalite (1987)
    Springer
    Physics and chemistry of minerals 14 (1987), S. 499-513 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Polarized single-crystal absorption and reflection spectra of fundamental modes in both the mid- and far-infrared are presented for microscopic crystals of forsterite and fayalite. All modes predicted by symmetry were observed for forsterite, but two B3u modes were not observed for fayalite. Consideration of previously determined frequency shifts for isotopically and chemically substituted olivines, along with symmetry analysis, produced a complete set of band assignments satisfying all constraints for forsterite. A plausible assingment was derived for fayalite by analogy. The frequency shifts from forsterite to fayalite are consistently small for bands assigned to SiO4 stretching and bending, moderate for rotations, and large for translations of M-site ions, suggesting that in olivine, SiO4 groups vibrate separately from the lattice. Allocating the bending and external modes among multiple continua in Kieffer's (1979c) model considerably improves prediction of quasiharmonic heat capacityC v and entropy for forsterite (∼1% discrepancy from 200–1000 K). The experimental entropy of fayalite is closely accounted for (1.8 to 0.1%) by summing lattice, electronic (from Burns' (1985) optical band assignment), and constant magnetic contributions above 200 K.S magnetic determined from the difference of the experimental and model lattice entropies shows inflection points at the two magnetic transition temperatures (23 and 66 K) and indicates that complete spin disorder is not achieved below 680 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308285
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  • 4
    Electronic Resource
    Electronic Resource
    A model for the irradiative coloration of smoky feldspar and the inhibiting influence of water (1985)
    Springer
    Physics and chemistry of minerals 12 (1985), S. 324-332 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Radiation-induced smoky color and associatedelectron paramagnetic resonance (EPR) signals develop only in potassium feldspar (KAlSi3O8) free of structurally bound molecular water. Fluid inclusion water does not influence coloration. The integrated intensity of each of the four bands (11,600, 16,200, 19,100, and 27,200 cm−1) in the optical absorption spectra are linearly correlated with the doubly-integrated intensity of a broad, asymmetric first derivative atg eff=2.027 in EPR spectra. In microcline, the EPR pattern is resolved into an asymmetric six-line pattern atg eff=2.024 and a single derivative atg eff=2.009 which, based on analogy to alkali-silicate glass, are due respectively to [SiO4/K+]2+ and a hole shared between two nonbonding oxygens on Si. We propose that structural water inhibits formation of smoky centers in feldspar by releasing atomic hydrogen during irradiation which destroys centers while diffusing towards a stable site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654342
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of Fe3+ and Fe2+ concentrations in feldspar by optical absorption and EPR spectroscopy (1984)
    Springer
    Physics and chemistry of minerals 11 (1984), S. 213-224 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Ferrous and ferric iron concentrations in feldspars with low total iron content (〈0.32 wt% total Fe) were determined from optical and electron paramagnetic resonance (EPR) spectra to better than ±15 percent of the amount present. Optical spectra indicate that Fe2+ occupies two distorted M-sites in plagioclases of intermediate structural state. The linear dependence of the Fe2+/Fe total ratio on An content demonstrates that Fe2+ substitutes for Ca (not Na) so that the number of Ca-sites is a principal factor in iron partitioning in plagioclase. EPR powder spectra show that the number of sites for Fe3+ depends on structural state rather than on plagioclase chemistry. The observed linear correspondence of EPR double-integrated intensities with optical peak areas shows that all Fe3+ is tetrahedrally coordinated in both plagioclase and disordered potassium feldspar. Microcline perthites show, in addition to tetrahedral Fe3+, a signal due to axially coordinated ferric iron, which we associate with formation of hematite inclusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308136
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  • 6
    Electronic Resource
    Electronic Resource
    Infrared spectroscopic investigation of hydroxyl in β-(Mg,Fe)2SiO4 and coexisting olivine: Implications for mantle evolution and dynamics (1993)
    Springer
    Physics and chemistry of minerals 19 (1993), S. 409-422 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Wadsleyite (β-(Mg,Fe)2SiO4) is a major constituent of the Earth's transition zone and is known to accommodate OH. The portion of the transition zone between 400–550 km could be an important source or sink for hydroxyl in plumes and slabs intersecting this region. Micro-infrared spectroscopy has been carried out on the β-phase and coexisting metastable olivine synthesized in a multianvil apparatus at 14 GPa and 1550–1650 K under hydrous conditions. Single-crystal and polycrystal specimens of both phases were analyzed in the 1800–8500 cm−1 frequency region to determine the speciation, abundances, and partitioning behavior of the hydrous components in coexisting β-phase and olivine. β-phase spectra consistently show three distinct OH bands at 3329, 3580, and 3615 cm−1. OH concentrations range from 10000–65000 H/106 Si. A strong positive correlation of grain size and extent of transformation with OH concentration in the β-phase indicates that grain-growth and transformation rates are enhanced in a hydrous environment. Olivine spectra are variable, but consistently show a prominent broad-band absorbance representing molecular H2O, consistent with the infrared signature of the starting material. OH concentrations in olivine range from 〈300–1400 H/106 Si. The highest OH concentrations measured for olivine and the β-phase may represent solubility limits, in which case the OH solubility ratio between these two phases is approximately 1∶40. Where both phases coexist and are undersaturated with OH, the partitioning ratio of OH between them is about 1∶100. The large solubility contrast between olivine and the β-phase suggests a mechanism for hydrating the transition zone via olivine carried down in subducting slabs. Plumes impinging on an OH-rich upper transition region could cause H2 or H2O to be released upon transformation of the β-phase to olivine, resulting in initiation of secondary upwellings. If dissolution of OH weakens the β-phase, and if OH is present in the mantle, the region between 400–550 km could be a zone of low viscosity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202978
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  • 7
    Electronic Resource
    Electronic Resource
    A structural phase-transition in K(Mg1−xCux)F3 perovskite (1996)
    Springer
    Physics and chemistry of minerals 23 (1996), S. 141-150 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract A complete solid-solution series between cubic (Pm 3 m) KMgF3 and tetragonal (I4/mcm) KCuF3 was synthesized at 730–735 °C in an inert atmosphere. X-ray powder-diffraction at room temperature shows that the transition between the cubic and tetragonal perovskite structures in the series K (Mg1−xCux) F3 occurs at x ∼ 0.6. Rietveld structure-refinements were done for selected compositions. In the cubic phase, all parameters are linear with composition up to the transition point. At the transition point, there is a strong discontinuity in the cell volume; this is strongly anisotropic with expansion along the a axes and contraction along the c axis due to a pronounced axial elongation of the (Mg, Cu) F6 octahedron that increases with increasing Cu content. The phase transition is first-order, with a discontinuity of ≈2% in the symmetry-breaking strain at xC. It is proposed that the phase transition in K (Mg, Cu) F3 is due to the onset of the cooperative Jahn-Teller effect. Compositional relationships for lattice vibrations in this solid solution were established using thin-film infrared spectroscopy. A phase transition occurring above 60 mole % KCuF3 is indicated by the appearance of one of the two modes expected for the tetragonal phase; the weaker mode is not resolved below 80 mole % KCuF3. Modes common to both structures vary smoothly and continuously across the binary; however, frequencies do not depend linearly on composition, nor is mode-softening discernable. Two-mode behaviour is observed only for the bending motion of the cubic phase, because this peak alone has non-overlapping end-member components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220725
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  • 8
    Electronic Resource
    Electronic Resource
    Infrared spectroscopy of CaGeO3 perovskite to 24 GPa and thermodynamic implications (1994)
    Springer
    Physics and chemistry of minerals 21 (1994), S. 78-84 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Far-infrared absorbance spectra were collected from CaGeO3 with a metastable orthorhombic perovskite structure from 0 to 24.4 GPa. The absorbance data are compatible with a reflectance spectrum which was collected at ambient conditions from a polished, densely compacted polycrystal. The reflectance spectrum shows 18 IR modes from 155 to 786 cm−1. A detailed model for the density of states constructed from these new data results in accurate calculation of heat capacity and new data on entropy. Peak positions increase linearly with pressure. Mode Grüneisen parameters (ranging from 0.72–1.56) decrease almost linearly with increasing mode frequency which is consistent with deformations of the oxygen sublattice dominating the lattice vibrations. Neither discontinuous changes in the number of modes nor in these frequencies nor in band widths are observed at pressures up to 24.4 GPa. Thus, conversion to the tetragonal phase at ∼12 GPa is not indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00205218
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  • 9
    Electronic Resource
    Electronic Resource
    Infrared reflectance spectra of fayalite, and absorption datafrom assorted olivines, including pressure and isotope effects (1997)
    Springer
    Physics and chemistry of minerals 24 (1997), S. 535-546 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Polarized single-crystal infrared (IR) reflectance spectra measured for synthetic fayalite (Fe2SiO4) possess all but one of the peaks mandated by symmetry plus a few weak bands attributable to overtones. Fayalite has a band at 86 cm−1, which is below the frequency range commonly examined, suggesting that vibrational spectra of ferrous minerals may need remeasuring. B2u polarizations were also measured for natural monticellite (nearly MgCaSiO4) and synthetic Mg2Si18O4. Thin film absorption data were collected for the above species, Co2SiO4, Mn2SiO4, Mg2SiO4, (Mg1.9Fe0.1)SiO4, Mg2GeO4 and Mn2GeO4. The relationships of IR peak positions (from these data and from previous single-crystal studies) with the inverse square root of the average cation mass were used to make band assignments, to estimate the positions for missing bands, and to determine which peaks are degenerate. The pressure dependencies of monticellite IR peaks were measured and resemble those of other olivines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690050069
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  • 10
    Electronic Resource
    Electronic Resource
    High-Pressure crystal chemistry of spinel (MgAl2O4) and magnetite (Fe3O4): Comparisons with silicate spinels (1986)
    Springer
    Physics and chemistry of minerals 13 (1986), S. 215-220 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract High-pressure crystal structures and compressibilities have been determined by x-ray methods for MgAl2O4 spinel and its isomorph magnetite, Fe3O4. The measured bulk moduli, K, of spinel and magnetite (assuming K′=4) are 1.94±0.06 and 1.86±0.05 Mbar, respectively, in accord with previous ultrasonic determinations. The oxygen u parameter, the only variable atomic position coordinate in the spinel structure (Fd3m, Z=8), decreases with pressure in MgAl2O4, thus indicating that the magnesium tetrahedron is more compressible than the aluminum octahedron. In magnetite the u parameter is unchanged, and both tetrahedron and octahedron display the 1.9 Mbar bulk modulus characteristic of the entire crystal. This behavior contrasts with that of nickel silicate spinel (γ-Ni2SiO4), in which the u parameter increases with pressure because the silicon tetrahedron is relatively incompressible compared to the nickel octahedron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308271
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