Locating hydrogen positions in the autunite mineral metatorbernite [Cu(UO2)2(PO4)2·8H2O]: A combined approach using neutron powder diffraction and computational modelling

Fiona M. MacIver-Jones, Polly Sutcliffe, Margaret C. Graham, Carole A. Morrison, Caroline A. Kirk*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Metatorbernite [Cu(UO2)2(PO4)2·8H2O] is a promising remediation material for environmental uranium contamination. Previous X-ray diffraction studies have been unable to definitively locate hydrogen positions within metatorbernite, which are key to determining the hydrogen-bond network that helps to stabilize the structure. Here, hydrogen positions have been determined using a combination of neutron powder diffraction and the computational modelling technique ab initio random structure searching (AIRSS). Atomic coordinates determined through Rietveld analysis of neutron powder diffraction data are in excellent agreement with the minimum energy configuration predicted by AIRSS; thus, simulations confirm that our proposed model likely represents the global minimum configuration. Two groups of water molecules exist within the metatorbernite structure: free water and copper-coordinating water. Free water molecules are held within the structure by hydrogen bonding only, whilst the coordinating water molecules bond to copper in the equatorial positions to produce a 4 + 2 Jahn-Teller octahedra. The successful agreement between neutron powder diffraction data and AIRSS suggests that this combined approach has excellent potential for the study of other (trans)uranium materials in which hydrogen bonding plays a key role in phase stability.

Original languageEnglish
Pages (from-to)963-972
Number of pages10
JournalIUCrJ
Volume8
Early online date2 Oct 2021
DOIs
Publication statusE-pub ahead of print - 2 Oct 2021

Keywords

  • AIRSS
  • Autunite
  • Computational modelling
  • Hydrogen positions
  • Inorganic chemistry
  • Metatorbernite
  • Mineral stability
  • Neutron powder diffraction

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