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Title: Structure–thermodynamics relationship of schoepite from first-principles

Journal Article · · Physical Chemistry Chemical Physics. PCCP
DOI:https://doi.org/10.1039/C9CP04117F· OSTI ID:1574710

The relationship between the structure and thermodynamic properties of schoepite, an important uranyl phase with formula [(UO2)8O2(OH)12]·12H2O formed upon corrosion of UO2, has been investigated within the framework of density functional perturbation theory (DFPT). Experimental crystallographic lattice parameters are well reproduced in this study using standard DFT. Phonon calculations within the quasi-harmonic approximation predict standard molar entropy and isobaric heat capacity of S0 = 179.60 J mol-1 K-1 and C0P = 157.4 J mol-1 K-1 at 298.15 K, i.e., ~6% and ~4% larger than existing DFPT-D2 calculations. The computed variation of the standard molar isobaric heat capacity with water content from schoepite (UO3·xH2O, x = 2.25) to dehydrated schoepite (x = 1) is predicted to be essentially linear along isotherms ranging from 100 to 500 K. Finally, these findings have important implications for the dehydration of layered uranyl corrosion phases and hygroscopic materials.

Research Organization:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Organization:
USDOE Office of Nuclear Energy (NE), Fuel Cycle Technologies (NE-5)
Grant/Contract Number:
AC04-94AL85000; NA0003525; NE0008788
OSTI ID:
1574710
Alternate ID(s):
OSTI ID: 1568931
Report Number(s):
SAND-2019-8118J; PPCPFQ; 677579; TRN: US2100018
Journal Information:
Physical Chemistry Chemical Physics. PCCP, Vol. 21, Issue 46; ISSN 1463-9076
Publisher:
Royal Society of ChemistryCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 3 works
Citation information provided by
Web of Science

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