CaO2: enthalpy of formation

4 accepted literature formation-enthalpy value(s) (model 3, DFT 1); Materials Project -212.9 kJ/mol-atom (mp-aaabkddr); OQMD -219.972 kJ/mol-atom (oqmd-1367693).

Systems: Ca–O

Literature values

Enthalpy of formation of CaO2 reported in the literature (4)
Value	Phase as printed	T (K)	Class	System	Source	Location
-219.667 kJ/mol-atom	CaO2(cr)	298.15	model	Ca–O	[1] Deffrennes 2020 cites Lindberg 2009 doi	Table 3, p. 17, row 13 report
-217.567 kJ/mol-atom	CaO2(cr)	298.15	model	Ca–O	[1] Deffrennes 2020 cites Liang 2018 doi	Table 3, p. 17, row 12 report
-216.033 kJ/mol-atom	CaO2(cr)	298.15	model	Ca–O	[1] Deffrennes 2020	Table 3, p. 17, row 11 report
-216.033 kJ/mol-atom	CaO2(cr)	298.15	DFT	Ca–O	[1] Deffrennes 2020 cites Pisch	Table 3, p. 17, row 14 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 CaO2
Value	Unit	Reading	Method (class, basis)	Effective
-219.667	kJ/mol-atom	0.01667	3.9 (model_calculated, calibrated)	3.9
-217.567	kJ/mol-atom	0.01667	3.9 (model_calculated, calibrated)	3.9
-216.033	kJ/mol-atom	0.01667	3.9 (model_calculated, calibrated)	3.9
-216.033	kJ/mol-atom	0.01667	9.966 (dft, calibrated)	9.966

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 CaO2
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaabkddr	-212.9	-2.20656	I4/mmm	0	0	no
OQMD	oqmd-1367693	-219.972	-2.27986	C2/c	0	0	yes

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

Guillaume Deffrennes, Noël Jakse, Cecilia M.S. Alvares, Ioana Nuta, Alain Pasturel, Alexandra Khvan et al., Thermodynamic modelling of the Ca–O system including 3rd generation description of CaO and CaO2, Calphad 69, 101764 (2020). doi:10.1016/j.calphad.2020.101764

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}
}