Thermal expansion of römerite under low-temperature conditions
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1.
California Institute of Technology
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2.
Brown University
- Editor:
- Gatta, G. Diego
Abstract
Römerite, a triclinic hydrous sulfate in the P1¯ space group with the chemical formula Fe²⁺Fe₂³⁺(SO₄)₄·14(H₂O), is of potential interest in studies of planetary environments, with particular relevance to Mars and the icy jovian satellites. Past work has indicated the presence of hydrous sulfates on said bodies, and the mixed-valence iron in römerite’s structure makes the mineral a worthwhile end-member composition in thermodynamic models. Such models should be constrained by measurements at the low temperatures relevant to the planetary environments in question. We characterized single crystals of römerite with time-domain Mössbauer spectroscopy, Raman spectroscopy, and X-ray diffraction methods. Through our X-ray diffraction experiment, we refined the unit-cell parameters of the crystal between 100 and 300 K. The resulting temperature-variant lattice parameters and volumes are reported and are fit by physical and empirical models of the thermal expansion coefficient. The physical model considered, a Debye model of thermal expansion, provides estimates of additional thermodynamic parameters: the ratio of the bulk modulus at 0 K and 1 bar to the thermodynamic Grüneisen parameter (K0,0K/γth), the volume at 0 K and 1 bar (V0,0K), and the Debye temperature (θD).
Copyright and License
© 2025 by the Mineralogical Society of America.
Acknowledgement
We thank Michael K. Takase and the Caltech X-ray Diffraction Facility (XRCF) for operation of the diffractometer. The XRCF is supported by the Dow Next Generation Instrumentation Grant and the Beckman Institute. We thank George Rossman for assistance in sample collection and for use of his laboratory in Raman spectroscopy measurements. We appreciate helpful discussions with Wolfgang Sturhahn, Benjamin Strozewski, and Cijin Zhou. We thank Ross Angel for valuable insights into his EoSFit7 software. We thank G. Diego Gatta, the associate editor assigned to our manuscript. Likewise, we appreciate the insightful reviews provided by Johannes Meusburger, Azzurra Zucchini, and an anonymous reviewer.
Funding
We thank NSF-CSEDI (EAR-2009935, -2303148) for supporting this work. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. Beamline 3-ID-B at the Advanced Photon Source was partially supported by COMPRES, the Consortium for Materials Properties Research in Earth Sciences under NSF cooperative agreement EAR-1606856.
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Additional details
- National Science Foundation
- EAR-2009935
- National Science Foundation
- EAR-2303148
- United States Department of Energy
- DE-AC02-06CH11357
- National Science Foundation
- EAR-1606856
- Accepted
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2024-10-23
- Available
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2024-10-31First online
- Caltech groups
- Seismological Laboratory, Division of Geological and Planetary Sciences (GPS)
- Publication Status
- Published