U3O8: enthalpy of formation

10 accepted literature formation-enthalpy value(s) (experimental 7, model 3); experimental median -324.982 kJ/mol-atom (n = 7); Materials Project -357.65 kJ/mol-atom (mp-aaaaaalw); OQMD -323.13 kJ/mol-atom (oqmd-5464).

Systems: O–U

Literature values

Enthalpy of formation of U3O8 reported in the literature (10)
Value	Phase as printed	T (K)	Class	System	Source	Location
-327.265 kJ/mol-atom	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Burdese 1958	Table 10, p. 8, row 20 report
-325.781 kJ/mol-atom ± 1.17913	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Popov 1957 doi	Table 10, p. 8, row 18 report
-324.983 kJ/mol-atom ± 0.228218	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Huber 1969 doi	Table 10, p. 8, row 17 report
-324.982 kJ/mol-atom ± 0.227273	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Cordfunke 1988	Table 10, p. 8, row 21 report
-324.869 kJ/mol-atom ± 0.760727	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Rand 1963	Table 10, p. 8, row 19 report
-324.64 kJ/mol-atom ± 0.608582	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Huber 1952 doi	Table 10, p. 8, row 16 report
-321.483 kJ/mol-atom	U3O8	298.15	experimental	O–U	[1] Chevalier 2002 cites Mixter 1912 doi	Table 10, p. 8, row 15 report
-325.22 kJ/mol-atom	U3O8 (s)	298.15	model	O–U	[2] Guéneau 2002	Table 4, p. 9, row 5 report
-324.979 kJ/mol-atom ± 0.218	U3O8 (s)	298.15	model	O–U	[2] Guéneau 2002 cites Grenthe 1992	Table 4, p. 9, row 6 report
-324.869 kJ/mol-atom	U3O8	298.15	model	O–U	[1] Chevalier 2002	Table 10, p. 8, row 22 report

Uncertainty budget

Components kept separate, in the value's unit (literature SCHEMA.md, UNCERTAINTY_CALIBRATION.md): effective = max(sqrt(max(printed, reading, method)^2 + composition^2 + conversion^2), scatter). The method floor is the robust between-study scatter of the method class in ORCHID (calibrated) or a documented prior; printed values and printed uncertainties are unchanged.

Uncertainty budget of the literature values of U3O8
Value	Unit	Printed	Reading	Method (class, basis)	Effective
-327.265	kJ/mol-atom		4.545e-6	3.5 (unknown, calibrated)	3.5
-325.781	kJ/mol-atom	1.179	4.545e-5	3.5 (unknown, calibrated)	3.5
-324.983	kJ/mol-atom	0.2282	4.545e-6	3.5 (unknown, calibrated)	3.5
-324.982	kJ/mol-atom	0.2273	0.004545	3.5 (unknown, calibrated)	3.5
-324.869	kJ/mol-atom	0.7607	4.545e-6	3.5 (unknown, calibrated)	3.5
-324.64	kJ/mol-atom	0.6086	4.545e-5	3.5 (unknown, calibrated)	3.5
-321.483	kJ/mol-atom		4.545e-6	3.5 (unknown, calibrated)	3.5
-325.22	kJ/mol-atom		5.000e-4	3.9 (model_calculated, calibrated)	3.9
-324.979	kJ/mol-atom	0.218	5.000e-4	3.9 (model_calculated, calibrated)	3.9
-324.869	kJ/mol-atom		4.545e-6	3.9 (model_calculated, calibrated)	3.9

DFT formation energies

Lowest-energy entries at this composition. Materials Project and OQMD use different energy references and are never averaged. 1 eV/atom = 96.485 kJ/mol-atom.

DFT formation energy of U3O8
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaaaaalw	-357.65	-3.7068	P-62m	0	0	no
OQMD	oqmd-5464	-323.13	-3.34902	Amm2	1.3093	0.0136	no

DFT sources: A. Jain et al., Commentary: The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002. doi:10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501-1509; S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010. doi:10.1007/s11837-013-0755-4 (CC BY 4.0);

Sources

P.-Y. Chevalier, E. Fischer, B. Cheynet, Progress in the thermodynamic modelling of the O–U binary system, Journal of Nuclear Materials 303, 1-28 (2002). doi:10.1016/s0022-3115(02)00813-9
C. Guéneau, M. Baichi, D. Labroche, C. Chatillon, B. Sundman, Thermodynamic assessment of the uranium–oxygen system, Journal of Nuclear Materials 304, 161-175 (2002). doi:10.1016/s0022-3115(02)00878-4

Please cite

R. Arróyave, J. Saal, D. Shin, ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23735569
R. Arróyave, J. Saal, D. Shin, ORCHID-Parity: DFT-vs-experiment formation-enthalpy benchmark (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23735943
R. Arróyave, J. Saal, D. Shin, ORCHID data: umbrella record of the ORCHID datasets (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23736065

Also cite the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work); A. Jain et al., The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002, https://doi.org/10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501, https://doi.org/10.1007/s11837-013-0755-4 and S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010, https://doi.org/10.1038/npjcompumats.2015.10 (CC BY 4.0); G. Kim, S. V. Meschel, P. Nash, W. Chen, Experimental formation enthalpies for intermetallic phases and other inorganic compounds, Scientific Data 4 (2017) 170162, https://doi.org/10.1038/sdata.2017.162; B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, https://doi.org/10.1016/j.calphad.2025.102833 (CC BY 4.0), and the original assessment named in each file. Version 1, machine-extracted: values were read by language-model readers constrained to quote their source and checked automatically, and the release was then audited on the printed pages by adversarial audits, an independent second review of fit-facing records and a preliminary human review of a frozen sample. Flags such as accepted and ESPEI-ready record screening results, not certification; known issues are listed in the release notes.

@misc{orchid_literature_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Values: thermodynamic and phase-equilibrium values read from the literature}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735569},
  url       = {https://doi.org/10.5281/zenodo.23735569},
  note      = {Version 1, machine-extracted}
}

@misc{orchid_dft_benchmark_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Parity: DFT-vs-experiment formation-enthalpy benchmark}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735943},
  url       = {https://doi.org/10.5281/zenodo.23735943},
  note      = {Version 1, machine-extracted}
}

@misc{orchid_data_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID data: umbrella record of the ORCHID datasets}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23736065},
  url       = {https://doi.org/10.5281/zenodo.23736065},
  note      = {Version 1, machine-extracted}
}