Crystal structure of magnetite under pressure |
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| Authors: | N Nakagiri M H Manghnani L C Ming S Kimura |
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| Institution: | 1. Hawaii Institute of Geophysics, University of Hawaii, 96822, Honolulu, HI, USA
2. National Institute for Research in Inorganic Materials, Niiharu-gun, Ibaraki, Japan
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| Abstract: | The crystal structure and the unit-cell parameters of magnetite have been studied at room temperature up to a pressure of 4.5 GPa using a diamond anvil cell and a four-circle X-ray diffractometer. The isothermal bulk modulus (K T ) and its pressure derivative (K' T ) determined by fitting the pressure-volume data to the Murnaghan equation of state are 181(2) GPa and 5.5(15), respectively. The positional parameter u does not vary significantly over the pressure range of this study. The linear compressibilities of the interatomic distances and the bulk moduli of the polyhedra have been calculated from the pressure dependences of the unit-cell edge a and the u parameter. The Bloch equation has been modified to derive a relationship between the Néel temperature and the parameter u. The modified Bloch equation gives a closer agreement with the experimental results than the Weisz equation. |
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