Spectroscopy of Minerals

Lehmann, Gerhard

doi:10.1002/bbpc.198200004

Cited by 5 publications

(1 citation statement)

References 60 publications

(19 reference statements)

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“…In our view all arguments based on the unrelaxed geometries of the pure lattice sites are inconclusive for the distortions which are decisive in this case. Indeed already for the case of considerably smaller size mismatch of Mn 2+ in diopside (Gaite 1975) the pseudosymmerry analysis was shown to lead to an erroneous assignment (Lehmann 1982).…”

Section: $2 Centersmentioning

confidence: 98%

The structures of three centers of trivalent iron in ?-quartz

Stegger

Lehmann

1989

Phys Chem Minerals

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Abstract. Trivalent iron is known to occur in amethysts in three different environments: substitutional with an as yet unidentified alkali ion in an adjacent interstitial site on the twofold axis (so-called $1 center), substitutional with a proton on one of the four oxygen neighbors ($2 center) and without detectable charge compensation (so-called I center because it was proposed to be in interstitial sites, but its nature is still disputed). The alkali ion in the Sz center was now identified as Li and the Li and Fe superhyperfine (shf) tensors were determined by electron paramagnetic resonance at low temperatures in samples of unusually high quality. The fine structure and ~H shf structure tensors for the $2 center with the proton on an oxygen with longer bond distance were evaluated and the geometry of the oxygen coordination was estimated by application of the superposition model. For the I center the 57Fe and zgsi shf splittings were determined and the evidence in favor of assignment to an interstitial site is reviewed.

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Section: $2 Centersmentioning

confidence: 98%

The structures of three centers of trivalent iron in ?-quartz

Stegger

Lehmann

1989

Phys Chem Minerals

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Interstitial Transition Metal Impurities as a Possible Cause of Enhanced Reactivities

Behner¹,

Elbers²,

Remme³

et al. 1986

Ber Bunsenges Phys Chem

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Trivalent ions of Fe, Cr and Mo are easily incorporated into CsCl‐type lattices. Evidently their geometries partly derive from those for divalent ions by exchange of a neutral molecule by hydroxyl or halide. In the ammonium halides hydrogen bonding manifests itself in predominance of low site symmetries and dynamic effects. Evidence for interstitial incorporation of di‐ and trivalent ions in quartz and isomorphous ABO4 compounds is also presented. EPR data for Fe3+ indicate simultaneous incorporation of O2− or OH− in the c‐axis channels. A kinetic reason for preferred interstitial incorporation is proposed. Enhanced mobilities of these as well as certain main constituents may also enhance the reactivities.

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Electron Paramagnetic Resonance of Mn²⁺ in Orthorhombic and Higher Symmetry Crystals

Jain

Lehmann

1990

Physica Status Solidi (b)

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Spectroscopy of Minerals

Cited by 5 publications

References 60 publications

The structures of three centers of trivalent iron in ?-quartz

The structures of three centers of trivalent iron in ?-quartz

Interstitial Transition Metal Impurities as a Possible Cause of Enhanced Reactivities

Electron Paramagnetic Resonance of Mn²⁺ in Orthorhombic and Higher Symmetry Crystals

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Spectroscopy of Minerals

Cited by 5 publications

References 60 publications

The structures of three centers of trivalent iron in ?-quartz

The structures of three centers of trivalent iron in ?-quartz

Interstitial Transition Metal Impurities as a Possible Cause of Enhanced Reactivities

Electron Paramagnetic Resonance of Mn2+ in Orthorhombic and Higher Symmetry Crystals

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Electron Paramagnetic Resonance of Mn²⁺ in Orthorhombic and Higher Symmetry Crystals