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Vibrational anisotropy of δ-(Al,Fe)OOH single crystals as probed by nuclear resonant inelastic X-ray scattering

Buchen, Johannes and Sturhahn, Wolfgang and Ishii, Takayuki and Jackson, Jennifer M. (2021) Vibrational anisotropy of δ-(Al,Fe)OOH single crystals as probed by nuclear resonant inelastic X-ray scattering. European Journal of Mineralogy, 33 (4). pp. 485-502. ISSN 1617-4011. doi:10.5194/ejm-33-485-2021.

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The formation of high-pressure oxyhydroxide phases spanned by the components AlOOH–FeOOH–MgSiO₂(OH)₂ in experiments suggests their capability to retain hydrogen in Earth's lower mantle. Understanding the vibrational properties of high-pressure phases provides the basis for assessing their thermal properties, which are required to compute phase diagrams and physical properties. Vibrational properties can be highly anisotropic, in particular for materials with crystal structures of low symmetry that contain directed structural groups or components. We used nuclear resonant inelastic X-ray scattering (NRIXS) to probe lattice vibrations that involve motions of ⁵⁷Fe atoms in δ-(Al_(0.87)Fe_(0.13))OOH single crystals. From the recorded single-crystal NRIXS spectra, we calculated projections of the partial phonon density of states along different crystallographic directions. To describe the anisotropy of central vibrational properties, we define and derive tensors for the partial phonon density of states, the Lamb–Mössbauer factor, the mean kinetic energy per vibrational mode, and the mean force constant of ⁵⁷Fe atoms. We further show how the anisotropy of the Lamb–Mössbauer factor can be translated into anisotropic displacement parameters for ⁵⁷Fe atoms and relate our findings on vibrational anisotropy to the crystal structure of δ-(Al,Fe)OOH. As a potential application of single-crystal NRIXS at high pressures, we discuss the evaluation of anisotropic thermal stresses in the context of elastic geobarometry for mineral inclusions. Our results on single crystals of δ-(Al,Fe)OOH demonstrate the sensitivity of NRIXS to vibrational anisotropy and provide an in-depth description of the vibrational behavior of Fe³⁺ cations in a crystal structure that may motivate future applications of NRIXS to study anisotropic vibrational properties of minerals.

Item Type:Article
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URLURL TypeDescription
Buchen, Johannes0000-0001-5671-5214
Sturhahn, Wolfgang0000-0002-9606-4740
Ishii, Takayuki0000-0002-1494-2141
Jackson, Jennifer M.0000-0002-8256-6336
Additional Information:© Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 31 October 2020 – Revised: 15 June 2021 – Accepted: 22 June 2021 – Published: 17 August 2021. Special issue statement: This article is part of the special issue “Probing the Earth: experiments and mineral physics at mantle depths”. It is not associated with a conference. We thank Thomas S. Toellner for assistance with NRIXS experiments and Lawrence M. Henling for help with single-crystal XRD. Johannes Buchen was supported by National Science Foundation's (NSF) Collaborative Studies of the Earth's Deep Interior under EAR-1161046 and EAR-2009935 awarded to Jennifer M. Jackson. This research used resources of the Advanced Photon Source (APS), 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. The beamline 3-ID-B at APS is partially supported by COMPRES, the Consortium for Materials Properties Research in Earth Sciences under NSF cooperative agreement EAR-1606856. We further thank two anonymous reviewers for their comments that helped to improve our manuscript. This research has been supported by the National Science Foundation's Collaborative Studies of the Earth's Deep Interior (grant nos. EAR-1161046 and EAR-2009935). Data availability: NRIXS spectra have been deposited as PHOENIX projects at the California Institute of Technology Research Data Repository. The data set is retrievable at (Buchen et al., 2021). Supplement: The supplement related to this article is available online at: Author contributions: JB and JMJ designed the study and performed NRIXS experiments. TI synthesized single crystals of δ-(Al,Fe)OOH and performed electron microprobe measurements. JB analyzed single-crystal XRD and NRIXS data, developed the tensor description, and wrote the manuscript. WS wrote and maintains the software PHOENIX. JMJ and WS validated NRIXS data analyses and results. All authors commented on the manuscript. The authors declare that they have no conflict of interest. Review statement: This paper was edited by Monika Koch-Müller and reviewed by two anonymous referees.
Group:Seismological Laboratory
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-06CH11357
Issue or Number:4
Record Number:CaltechAUTHORS:20210930-224444188
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Official Citation:Buchen, J., Sturhahn, W., Ishii, T., and Jackson, J. M.: Vibrational anisotropy of δ-(Al,Fe)OOH single crystals as probed by nuclear resonant inelastic X-ray scattering, Eur. J. Mineral., 33, 485–502,, 2021
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111148
Deposited By: Tony Diaz
Deposited On:04 Oct 2021 20:42
Last Modified:04 Oct 2021 20:42

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