Reduced partition function ratios of iron and oxygen in goethite

Blanchard, M. and Dauphas, N. and Hu, M. Y. and Roskosz, M. and Alp, E. E. and Golden, D. C. and Sio, C. K. and Tissot, F. L. H. and Zhao, J. and Gao, L. and Morris, R. V. and Fornace, M. and Floris, A. and Lazzeri, M. and Balan, E. (2015) Reduced partition function ratios of iron and oxygen in goethite. Geochimica et Cosmochimica Acta, 151 . pp. 19-33. ISSN 0016-7037

Documents
22788 blanchard_geochimica_cosmochimica_acta_2014_1-s2 0-S0016703714007157-main.pdf

Request a copy
22788 Article_Fe_Beta_Goethite_revised (002).pdf
[img]
[Download]
[img] PDF
22788 blanchard_geochimica_cosmochimica_acta_2014_1-s2 0-S0016703714007157-main.pdf - Whole Document
Restricted to Repository staff only

961kB
[img]
Preview
PDF
22788 Article_Fe_Beta_Goethite_revised (002).pdf - Whole Document

1MB
Item Type:Article
Item Status:Live Archive

Abstract

First-principles calculations based on the density functional theory (DFT) with or without the addition of a Hubbard U correction, are performed on goethite in order to determine the iron and oxygen reduced partition function ratios (β-factors). The calculated iron phonon density of states (pDOS), force constant and β-factor are compared with reevaluated experimental β-factors obtained from Nuclear Resonant Inelastic X-ray Scattering (NRIXS) measurements. The reappraisal of old experimental data is motivated by the erroneous previous interpretation of the low- and high-energy ends of the NRIXS spectrum of goethite and jarosite samples (Dauphas et al., 2012). Here the NRIXS data are analyzed using the SciPhon software that corrects for non-constant baseline. New NRIXS measurements also demonstrate the reproducibility of the results. Unlike for hematite and pyrite, a significant discrepancy remains between DFT, NRIXS and the existing Mössbauer-derived data. Calculations suggest a slight overestimation of the NRIXS signal possibly related to the baseline definition. The intrinsic features of the samples studied by NRIXS and Mössbauer spectroscopy may also contribute to the discrepancy (e.g., internal structural and/or chemical defects, microstructure, surface contribution). As for oxygen, DFT results indicate that goethite and hematite have similar β-factors, which suggests almost no fractionation between the two minerals at equilibrium.

Keywords:geophysics, strongly correlated materials, bmjconvert, NotOAChecked
Subjects:F Physical Sciences > F343 Computational Physics
F Physical Sciences > F660 Geophysics
F Physical Sciences > F642 Geoscience
Divisions:College of Science > School of Mathematics and Physics
Related URLs:
ID Code:22788
Deposited On:10 Apr 2016 17:48

Repository Staff Only: item control page