57 Fe Mössbauer isomer shift of pure iron and iron oxides at high pressure—An experimental and theoretical study - Archive ouverte HAL Access content directly
Journal Articles Journal of Chemical Physics Year : 2021

57 Fe Mössbauer isomer shift of pure iron and iron oxides at high pressure—An experimental and theoretical study

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Wenli Bi
  • Function : Author
Jiyong Zhao
  • Function : Author
Michael Hu
  • Function : Author
Esen Alp
  • Function : Author

Abstract

The 57Fe isomer shift (IS) of pure iron has been measured up to 100 GPa using synchrotron Mössbauer spectroscopy in the time domain. Apart from the expected discontinuity due to the α → ε structural and spin transitions, the IS decreases monotonically with increasing pressure. The absolute shifts were reproduced without semi-empirical calibrations by periodic density functional calculations employing extensive localized basis sets with several common density functionals. However, the best numerical agreement is obtained with the B1WC hybrid functional. Extension of the calculations to 350 GPa, a pressure corresponding to the Earth’s inner core, predicted the IS range of 0.00 to −0.85 mm/s, covering the span from Fe(0) to Fe(VI) compounds measured at ambient pressure. The calculations also reproduced the pressure trend from polymorphs of prototypical iron oxide minerals, FeO and Fe2O3. Analysis of the electronic structure shows a strong donation of electrons from oxygen to iron at high pressure. The assignment of formal oxidation to the Fe atom becomes ambiguous under this condition.

Dates and versions

hal-03265404 , version 1 (20-06-2021)

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Jacques Desmarais, Wenli Bi, Jiyong Zhao, Michael Hu, Esen Alp, et al.. 57 Fe Mössbauer isomer shift of pure iron and iron oxides at high pressure—An experimental and theoretical study. Journal of Chemical Physics, 2021, 154 (21), pp.214104. ⟨10.1063/5.0048141⟩. ⟨hal-03265404⟩
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