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Crystallographic preferred orientation in wüstite (FeO) through the cubic-to-rhombohedral phase transition |
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| Authors: | P Kaercher S Speziale L Miyagi W Kanitpanyacharoen H-R Wenk |
| Institution: | 1. Department of Earth and Planetary Science, University of California, Berkeley, CA, 94720, USA 2. Helmholtz Center, GFZ German Research Centre for Geosciences, 14473, Potsdam, Germany 3. Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, 84112, USA |
| Abstract: | Magnesiowüstite, (Mg0.08Fe0.88)O, and wüstite, Fe0.94O, were compressed to ~36?GPa at ambient temperature in the diamond anvil cell (DAC) at the Advanced Light Source. X-ray diffraction patterns were taken in situ in radial geometry in order to study the evolution of crystallographic preferred orientation through the cubic-to-rhombohedral phase transition. Under uniaxial stress in the DAC, {100}c planes aligned perpendicular to the compression direction. The {100}c in cubic became { $\left\{ {10\bar 14} \right\}$ }r in rhombohedral and remained aligned perpendicular to the compression direction. However, the {101}c and {111}c planes in the cubic phase split into { ${10{\bar{1}}4}$ }r and { ${11{\bar{2}}0}$ }r, and (0001)r and { ${10{\bar{1}}1}$ }r, respectively, in the rhombohedral phase. The { ${11{\bar{2}}0}$ }r planes preferentially aligned perpendicular to the compression direction while { ${10{\bar{1}}4}$ }r oriented at a low angle to the compression direction. Similarly, { ${10{\bar{1}}1}$ }r showed a slight preference to align more closely perpendicular to the compression direction than (0001)r. This variant selection may occur because the 〈 ${10{\bar{1}}4}$ 〉r and 0001]r directions are the softer of the two sets of directions. The rhombohedral texture distortion may also be due to subsequent deformation. Indeed, polycrystal plasticity simulations indicate that for preferred { ${10{\bar{1}}4}$ }〈 ${1{\bar{2}}10}$ 〉r and { ${11{\bar{2}}0}$ }〈 ${{\bar{1}}101}$ 〉r slip and slightly less active { ${10{\bar{1}}1}$ }〈 ${{\bar{1}}2{\bar{1}}0}$ 〉r slip, the observed texture pattern can be obtained. |
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