Thermodynamic investigations of the uranium-molybdenum-oxygen system by a coupling of density functional theory and CALPHAD methodologies

• This paper examines the development of a consistent thermodynamic model for the uranium (U) - molybdenum (Mo) - oxygen (0) system for incorporation into the Thermodynamics of Advanced Fuels - International Database (TAF-ID). Phase diagram data and thermodynamic properties from the literature are reviewed. Density functional theory ab initio calculations at 0 K are combined with a quasi -harmonic statistical thermodynamic model to calculate thermodynamic functions (e.g., integral Delta H-298.15K(0), S-298.15K(0), and C-p(0) (T))of the relevant ternary compounds when little or no thermodynamic literature data are available. A CALPHAD method is employed to derive a model describing the Gibbs energy functions for all the relevant ternary compounds, the liquid phase, and the gas phase of the U-Mo-O system. A consistent thermodynamic model is obtained for the Mo-U-0 system with a special emphasis placed on the oxygen rich portion of the ternary (ie., MoO2-UO2-O). Finally, supporting binary and pseudo binary diagrams (e.g., Mo-O, UO2-MoO3 and UO3-MoO3) are computed and compared to literature data.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Annan teknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Other Engineering and Technologies (hsv//eng)

Nyckelord

Mo-U-O

Thermodynamic description

DFT

Ab initio

Quasi-harmonic models

CALPHAD

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