Optically detected magnetic resonance of the (AlO<sub>4</sub>)<sup>0</sup>centre in crystalline quartz

Meyer, B. K.; Lohse, F.; Spaeth, J.‐M.; Weil, J. A.

doi:10.1088/0022-3719/17/1/008

Cited by 37 publications

(16 citation statements)

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“…The smoky coloration intensifies with increase in the radiation dose. Previous experimental and theoretical studies have shown that the smoky color of quartz is attributable to the formation of the [AlO 4 ] 0 center during irradiation (Meyer et al 1984;Walsby et al 2003;To et al 2005).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic and magnetic properties of surface Fe3+ species on quartz: effects of gamma-ray irradiation and implications for aerosol–radiation interactions

Sivaramaiah

Pan

2012

Phys Chem Minerals

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Samples of a natural amethyst, pulverized in air, and irradiated for gamma-ray doses from 0.14 to 70 kGy, have been investigated by powder electron paramagnetic resonance (EPR) spectroscopy from 90 to 294 K. The powder EPR spectra show that the surface Fe 3? species on the gamma-ray-irradiated quartz differ from its counterpart without irradiation in both the effective g value and the observed line shape, suggesting marked radiation effects. This suggestion is supported by quantitatively determined thermodynamic properties, magnetic susceptibility, relaxation times, and geometrical radius. In particular, the surface Fe 3? species on gamma-ray-irradiated quartz has larger Gibbs and activation energies than its non-irradiated counterpart, suggesting radiation-induced chemical reactions. The shorter phase-memory time (T m ) but longer spin-lattice relaxation time (T 1 ) of the surface Fe 3? species on the gamma-ray-irradiated quartz than that without irradiation indicate stronger dipolar interactions in the former. Moreover, the calculated geometrical radius of the surface Fe 3? species on the gamma-ray-irradiated quartz is three orders of magnitude larger than that of its counterpart on the as-is sample. These results provide new insights into radiation-induced aerosol nucleation, with relevance to atmospheric cloud formation and global climate changes.

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Section: Resultsmentioning

confidence: 99%

Thermodynamic and magnetic properties of surface Fe3+ species on quartz: effects of gamma-ray irradiation and implications for aerosol–radiation interactions

Sivaramaiah

Pan

2012

Phys Chem Minerals

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“…1,2 The corresponding neutral Al defect center (hereafter also denoted [AlO 4 ] 0 ) is magnetically active, and has been the subject of extensive characterization by electron paramagnetic resonance (EPR), [3][4][5] also in combination with absorption spectroscopy. [6][7][8] From the theory side, it has been recognized that the reproduction of the experimentally observed features of the [AlO 4 ] 0 center is subordinate to a correct description of the hole localization properties. Since early density-functional theory (DFT) calculations using (semi)local density functionals gave a wrong picture, predicting the hole to be delocalized over all the four Al nearest-neighbor O atoms, [9][10][11] this problem has been identified as a challenging testing ground for novel density-functional methods.…”

Section: Introductionmentioning

confidence: 99%

Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

Gerosa

Valentin

Bottani

et al. 2015

The Journal of Chemical Physics

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Articles you may be interested inDefect calculations in semiconductors through a dielectric-dependent hybrid DFT functional: The case of oxygen vacancies in metal oxides The Journal of Chemical Physics 143, 134702 (2015) We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO 2 , using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid functionals has been shown to be determinant for properly capturing the hole localization, this problem constitutes a prototypical benchmark for the accuracy of the method, allowing one to assess to what extent self-interaction effects are avoided. We obtain good results in terms of description of the charge localization and structural distortion around the Al center, improving with respect to the more popular B3LYP hybrid-functional approach.We also discuss the accuracy of computed hyperfine parameters, by comparison with previous calculations based on other self-interaction-free methods, as well as experimental values. We discuss and rationalize the limitations of our approach in computing defect-related excitation energies in lowdielectric-constant insulators. C 2015 AIP Publishing LLC.[http://dx

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“…The error may be as high as a factor of 3. Analogous measurements for the optical absorption due to the smoky quartz centers [14] …”

Section: Resultsmentioning

confidence: 99%

A Hole Center Causing Rose Coloration in AlPO₄ and GaPO₄

Requardt

Lehmann

1985

Physica Status Solidi (b)

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I n synthetic AlPO, crystals and Sn-doped GaPO, hole centers'localized on an oxygen showing an almost isotropic hyperfine splitting from a 31P nucleus are observed after X-ray irradiation and analyzed by EPR. They are evidently caused by substitution of A1 and Ga, respectively, bya divalent cation, most likely Mg2+. From the variation of the EPR linewidths with temperature an activation energy of 19 kJ/mole for thermal hopping of the hole is found in AIPO,. These centers cause a rose coloration and the first absorption band in AlPO, has an oscillator strength near 0.3, in the same range as for the smoky quartz centers. It is interpreted as arising from optical transfer of the hole within the PO, unit. Thermoluminescence emission is observed with destruction of the centers in AlPO,. From glow curves an activation energy of 136 kJ/mole is obtained which in this case represents the distance of the hole from the valence band. The properties of the center in AlPO, are compared to those of a similar center in certain natural rose-colored quartz crystals.I n synthetischen AlP0,-Kristallen und Sn-dotiertem GaPO, werden an einem Sauerstoff lokalisierte Lochzentren mit einer fast isotropen Hyperfeinaufspaltung durch einen *lP-Hern nach Rontgenbestrahlung mittels EPR beobachtet und analysiert. Sie werden offenbar durch Substitution eines A1 bzw. Ga durch ein zweiwertiges Kation, vermutlich MgS+, verureacht. Aus der Temperaturabhingigkeit der EPR-Linienbreiten in AIPO, wird eine Aktivierungsenergie von 19 kJ/Mol fur das thermische Hupfen des Lochs bestimmt. Diese Zentren verursachen eine rosa Farbe, und die erste Absorptionsbande in AIPO, hat eine Oszillatorenstarke von etwa 0,3, ahnlich der im Rauchquarzzentrum. Mit der Zerstorung dieser Zentren ist in AlPO, eine Thermolumineszenzemission zu beobachten, aus der der Abstand des Defektelektrons vom Valenzband zu 136 kJ/Mol bestimmt wird. Die Eigenschaften dieses Zentrums in AlPO, werden mit denen fur ein ahnliches Zentrum in manchen rosafarbenen natiirlichen Quarzen verglichen.

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Optically detected magnetic resonance of the (AlO₄)⁰centre in crystalline quartz

Cited by 37 publications

References 9 publications

Thermodynamic and magnetic properties of surface Fe3+ species on quartz: effects of gamma-ray irradiation and implications for aerosol–radiation interactions

Thermodynamic and magnetic properties of surface Fe3+ species on quartz: effects of gamma-ray irradiation and implications for aerosol–radiation interactions

Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

A Hole Center Causing Rose Coloration in AlPO₄ and GaPO₄

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Optically detected magnetic resonance of the (AlO4)0centre in crystalline quartz

Cited by 37 publications

References 9 publications

Thermodynamic and magnetic properties of surface Fe3+ species on quartz: effects of gamma-ray irradiation and implications for aerosol–radiation interactions

Thermodynamic and magnetic properties of surface Fe3+ species on quartz: effects of gamma-ray irradiation and implications for aerosol–radiation interactions

Communication: Hole localization in Al-doped quartz SiO2 within ab initio hybrid-functional DFT

A Hole Center Causing Rose Coloration in AlPO4 and GaPO4

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Optically detected magnetic resonance of the (AlO₄)⁰centre in crystalline quartz

A Hole Center Causing Rose Coloration in AlPO₄ and GaPO₄