A Caltech Library Service

Melting and phase relations of Fe-Ni-Si determined by a multi-technique approach

Dobrosavljevic, Vasilije V. and Zhang, Dongzhou and Sturhahn, Wolfgang and Zhao, Jiyong and Toellner, Thomas S. and Chariton, Stella and Prakapenka, Vitali B. and Pardo, Olivia S. and Jackson, Jennifer M. (2022) Melting and phase relations of Fe-Ni-Si determined by a multi-technique approach. Earth and Planetary Science Letters, 584 . Art. No. 117358. ISSN 0012-821X. doi:10.1016/j.epsl.2021.117358.

[img] MS Word - Supplemental Material
See Usage Policy.

[img] Video (MPEG) (Video. XRD 2D images (hot and cold) for burst heating run D1P2S3) - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


Many studies have suggested silicon as a candidate light element for the cores of Earth and Mercury. However, the effect of silicon on the melting temperatures of core materials and thermal profiles of cores is poorly understood, due to disagreements among melt detection techniques, uncertainties in sample pressure evolution during heating, and sparsity of studies investigating the combined effects of nickel and silicon on the phase diagram of iron. In this study we develop a multi-technique approach for measuring the high-pressure melting and solid phase relations of iron alloys and apply it to Fe_(0.8)Ni_(0.1)Si_(0.1) (Fe-11wt%Ni-5.3wt%Si), a composition compatible with recent estimates for the cores of Earth and Mercury. This approach combines results (20-83 GPa) from two atomic-level techniques: synchrotron Mössbauer spectroscopy (SMS) and synchrotron x-ray diffraction (XRD). Melting is independently detected by the loss of the Mössbauer signal, produced exclusively by solid-bound iron nuclei, and the onset of a liquid diffuse x-ray scattering signal. The use of a burst heating and background updating method for quantifying changes in the reference background during heating facilitates the determination of liquid diffuse signal onsets and leads to strong reproducibility and excellent agreement in melting temperatures determined separately by the two techniques. XRD measurements additionally constrain the hcp-fcc phase boundary and in-situ pressure evolution of the samples during heating. We apply our updated thermal pressure model to published SMS melting data on fcc-Fe and fcc-Fe_(0.9)Ni_(0.1) to precisely evaluate the effect of silicon on melting temperatures. We find that the addition of 10 mol% Si to Fe_(0.9)Ni_(0.1) reduces melting temperatures by ∼250 K at low pressures (<60 GPa) and flattens the hcp-fcc phase boundary. Extrapolating our results, we constrain the location of the hcp-fcc-liquid quasi-triple point at 147±14 GPa and 3140±90 K, which implies a melting temperature reduction of 500 K compared with Fe_(0.9)Ni_(0.1). The results demonstrate the advantages of combining complementary experimental techniques in investigations of melting under extreme conditions.

Item Type:Article
Related URLs:
URLURL TypeDescription
Dobrosavljevic, Vasilije V.0000-0002-3710-2188
Zhang, Dongzhou0000-0002-6679-892X
Sturhahn, Wolfgang0000-0002-9606-4740
Zhao, Jiyong0000-0002-0777-3626
Chariton, Stella0000-0001-5522-0498
Prakapenka, Vitali B.0000-0001-9270-2330
Pardo, Olivia S.0000-0003-3964-9272
Jackson, Jennifer M.0000-0002-8256-6336
Additional Information:© 2021 Elsevier. Received 30 May 2021, Revised 6 December 2021, Accepted 24 December 2021, Available online 17 March 2022, Version of Record 17 March 2022. We thank both Lisa Mauger and Caitlin Murphy for sample synthesis. We are grateful to the National Science Foundation (NSF-EAR-1727020, NSF-EAR-CSEDI-2009935) for financial support of this research. GeoSoilEnviroCARS and Sector 3 operations are partially supported by COMPRES (NSF-EAR-1661511). GeoSoilEnviroCARS is supported by the National Science Foundation – Earth Sciences (NSF-EAR-1634415) and Department of Energy-GeoSciences (DE-FG02-94ER14466). Use of APS is supported by the U.S. DOE Office of Science (DE-AC02-06CH11357). We thank two anonymous reviewers for their constructive comments and Dr. James Badro for handling the manuscript. CRediT authorship contribution statement. Vasilije V. Dobrosavljevic: Conceptualization, Formal analysis, Investigation, Methodology, Software, Visualization, Writing – original draft, Writing – review & editing. Dongzhou Zhang: Investigation, Methodology, Software, Writing – review & editing. Wolfgang Sturhahn: Investigation, Software, Writing – review & editing. Jiyong Zhao: Methodology. Thomas S. Toellner: Methodology, Writing – review & editing. Stella Chariton: Methodology. Vitali B. Prakapenka: Methodology, Writing – review & editing. Olivia S. Pardo: Investigation, Writing – review & editing. Jennifer M. Jackson: Conceptualization, Funding acquisition, Investigation, Methodology, Project administration, Supervision, Writing – review & editing. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-94ER14466
Department of Energy (DOE)DE-AC02-06CH11357
Subject Keywords:high-pressure melting; Mössbauer spectroscopy; X-ray diffraction; silicon; iron alloys; terrestrial cores
Record Number:CaltechAUTHORS:20220412-932056000
Persistent URL:
Official Citation:Vasilije V. Dobrosavljevic, Dongzhou Zhang, Wolfgang Sturhahn, Jiyong Zhao, Thomas S. Toellner, Stella Chariton, Vitali B. Prakapenka, Olivia S. Pardo, Jennifer M. Jackson, Melting and phase relations of Fe-Ni-Si determined by a multi-technique approach, Earth and Planetary Science Letters, Volume 584, 2022, 117358, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114271
Deposited By: George Porter
Deposited On:13 Apr 2022 17:29
Last Modified:13 Apr 2022 17:29

Repository Staff Only: item control page