An Ultradense Polymorph of Rutile with Seven-Coordinated Titanium from the Ries Crater
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- Ahmed El Goresy
- Max-Planck-Institut für Chemie, J. Joachim-Becher-Weg 27, 55128 Mainz, Germany.2Guangzhou Institute of Geochemistry, Chinese Academy of Science, Guangzhou, 510640, China.3Theoretical Geochemistry Program, Institute of Earth Sciences, Uppsala University, 75236 Uppsala, Sweden.4Laboratoire de Sciences de la Terre, Ecole Normale Supérieur de Lyon, 69364 Lyon, France.
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- Ming Chen
- Max-Planck-Institut für Chemie, J. Joachim-Becher-Weg 27, 55128 Mainz, Germany.2Guangzhou Institute of Geochemistry, Chinese Academy of Science, Guangzhou, 510640, China.3Theoretical Geochemistry Program, Institute of Earth Sciences, Uppsala University, 75236 Uppsala, Sweden.4Laboratoire de Sciences de la Terre, Ecole Normale Supérieur de Lyon, 69364 Lyon, France.
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- Günther Graup
- Max-Planck-Institut für Chemie, J. Joachim-Becher-Weg 27, 55128 Mainz, Germany.2Guangzhou Institute of Geochemistry, Chinese Academy of Science, Guangzhou, 510640, China.3Theoretical Geochemistry Program, Institute of Earth Sciences, Uppsala University, 75236 Uppsala, Sweden.4Laboratoire de Sciences de la Terre, Ecole Normale Supérieur de Lyon, 69364 Lyon, France.
書誌事項
- 公開日
- 2001-08-24
- DOI
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- 10.1126/science.1062342
- 公開者
- American Association for the Advancement of Science (AAAS)
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説明
<jats:p>We report the discovery of an ultradense post-rutile polymorph of titanium dioxide in shocked gneisses of the Ries crater in Germany. The microscopic diagnostic feature is intense blue internal reflections in crossed polarizers in reflected light. X-ray diffraction studies revealed a monoclinic lattice, isostructural with the baddeleyite ZrO<jats:sub>2</jats:sub>polymorph, and the titanium cation is coordinated with seven oxygen anions. The cell parameters are as follows:<jats:italic>a</jats:italic>= 4.606(2) angstroms,<jats:italic>b</jats:italic>= 4.986(3) angstroms,<jats:italic>c</jats:italic>= 4.933(3) angstroms, β (angle between<jats:italic>c</jats:italic>and<jats:italic>a</jats:italic>axes) = 99.17(6)°; space group<jats:italic>P2</jats:italic><jats:sub>1</jats:sub><jats:italic>/c</jats:italic>; density = 4.72 grams per cubic centimeter, where the numbers in parentheses are standard deviations in the last significant digits. This phase is 11% denser than rutile. The mineral is sensitive to x-ray irradiation and tends to invert to rutile. The presence of baddeleyite-type TiO<jats:sub>2</jats:sub>in the shocked rocks indicates that the peak shock pressure was between 16 and 20 gigapascals, and the post-shock temperature was much lower than 500°C.</jats:p>
収録刊行物
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- Science
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Science 293 (5534), 1467-1470, 2001-08-24
American Association for the Advancement of Science (AAAS)
