Universität zu Köln

Chen, Huawei, Shim, Sang-Heon, Leinenweber, Kurt, Prakapenka, Vitali, Meng, Yue and Prescher, Clemens (2018). Crystal structure of CaSiO3 perovskite at 28-62 GPa and 300 K under quasi-hydrostatic stress conditions. Am. Miner., 103 (3). S. 462 - 469. CHANTILLY: MINERALOGICAL SOC AMER. ISSN 1945-3027

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Abstract

To find the thermodynamically stable crystal structure of CaSiO3 perovskite (CaPv) at high pressure and 300 K, we have conducted synchrotron X-ray diffraction (XRD) on thermally stress-annealed samples in a Ne pressure medium in the diamond-anvil cell at 28-62 GPa. Rietveld refinements of the diffraction patterns are significantly improved in fitting the positions and intensities of the split lines of CaPv if the starting model is a tetragonal perovskite-type structure with the SiO6 octahedral rotation around the tetragonal c-axis. The result is in contrast with other previous experiments, but is consistent with first-principles calculations, reconciling the discrepancy between computations and experiments on the crystal structure of CaPv. We attribute the observed difference to the formation of the thermodynamically more stable phase under improved stress conditions in our experiments. Our fitting shows that the bulk modulus of CaPv is 223 +/- 6 GPa when its pressure derivative fixed to 4, which is also consistent with first-principles calculations. The previous observations of the diffraction patterns of CaPv inconsistent with the first-principles studies could be due to the formation of a metastable crystal structure of CaPv under elevated deviatoric stresses.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Chen, Huawei UNSPECIFIED UNSPECIFIED UNSPECIFIED Shim, Sang-Heon UNSPECIFIED UNSPECIFIED UNSPECIFIED Leinenweber, Kurt UNSPECIFIED UNSPECIFIED UNSPECIFIED Prakapenka, Vitali UNSPECIFIED UNSPECIFIED UNSPECIFIED Meng, Yue UNSPECIFIED UNSPECIFIED UNSPECIFIED Prescher, Clemens UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-193115
DOI:	10.2138/am-2018-6087
Journal or Publication Title:	Am. Miner.
Volume:	103
Number:	3
Page Range:	S. 462 - 469
Date:	2018
Publisher:	MINERALOGICAL SOC AMER
Place of Publication:	CHANTILLY
ISSN:	1945-3027
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language EQUATION-OF-STATE; LOWERMOST MANTLE CONDITIONS; LASER-HEATING SYSTEM; X-RAY-DIFFRACTION; PHASE-TRANSITION; HIGH-PRESSURE; STABILITY; ELASTICITY; PLATINUM; BEHAVIOR Multiple languages Geochemistry & Geophysics; Mineralogy Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/19311