Al2Ca: enthalpy of formation

18 accepted literature formation-enthalpy value(s) (experimental 8, model 5, DFT 5); experimental median -32.35 kJ/mol-atom (n = 8); Materials Project -32.104 kJ/mol-atom (mp-aaaaadom); OQMD -32.307 kJ/mol-atom (oqmd-5774).

Systems: Al–Ca

Literature values

Enthalpy of formation of Al2Ca reported in the literature (18)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-34.3 kJ/mol-atom ± 3.5	C15-Al2Ca	298.15	experimental	Experiment	Al–Ca	[1] Ozturk 2005 cites Notin 1982 doi	Table IV, p. 5, row 21 report
-34.3 kJ/mol-atom ± 3.5	Al2Ca	800	experimental	Emf	Al–Ca	[2] ISLAM 2005 cites ref. 35	Table V, p. 9, row 3 report
-33.4 kJ/mol-atom ± 0.6	C15-Al2Ca	298.15	experimental	Experiment	Al–Ca	[1] Ozturk 2005 cites Notin 1995 doi	Table IV, p. 5, row 20 report
-33.4 kJ/mol-atom ± 0.6	Al2Ca	1038	experimental	Precipitation Calorimetry	Al–Ca	[2] ISLAM 2005 cites ref. 31	Table V, p. 9, row 2 report
-31.3 kJ/mol-atom ± 0.5	C15-Al2Ca	298.15	experimental	Experiment	Al–Ca	[1] Ozturk 2005 cites Veleckis 1981 doi	Table IV, p. 5, row 22 report
-31.28 kJ/mol-atom ± 0.46	Al2Ca	788	experimental	Hydrogen Titration	Al–Ca	[2] ISLAM 2005 cites ref. 34	Table V, p. 9, row 1 report
-29.4 kJ/mol-atom ± 0.9	C15-Al2Ca	298.15	experimental	Experiment	Al–Ca	[1] Ozturk 2005 cites Kevorkov 2001	Table IV, p. 5, row 19 report
-29.4 kJ/mol-atom ± 0.9	Al2Ca	298.15	experimental	Dissolution Calorimetry	Al–Ca	[2] ISLAM 2005 cites ref. 26	Table V, p. 9, row 4 report
-41.732 kJ/mol-atom	C15-Al2Ca		model	thermodynamic evaluation	Al–Ca	[1] Ozturk 2005 cites Itkin 1988 doi	Table IV, p. 5, row 15 report
-32.185 kJ/mol-atom	C15-Al2Ca		model	thermodynamic evaluation	Al–Ca	[1] Ozturk 2005 cites Ozturk 2002 doi	Table IV, p. 5, row 16 report
-29.7 kJ/mol-atom	C15-Al2Ca		model	thermodynamic evaluation	Al–Ca	[1] Ozturk 2005 cites Kevorkov 2001	Table IV, p. 5, row 17 report
-29.7 kJ/mol-atom	Al2Ca	800	model	Assessed	Al–Ca	[2] ISLAM 2005 cites ref. 26	Table V, p. 9, row 5 report
-29.28 kJ/mol-atom	Al2Ca	298.15	model	Calculated in this work	Al–Ca	[2] ISLAM 2005	Table V, p. 9, row 6 report
-36.604 kJ/mol-atom	C15-Al2Ca	0	DFT	WIEN2k	Al–Ca	[1] Ozturk 2005	Table IV, p. 5, row 11 report
-36.272 kJ/mol-atom	C15-Al2Ca	0	DFT	VASP	Al–Ca	[1] Ozturk 2005	Table IV, p. 5, row 13 report
-34.018 kJ/mol-atom	C15-Al2Ca	0	DFT	VASP	Al–Ca	[1] Ozturk 2005	Table IV, p. 5, row 14 report
-32.136 kJ/mol-atom	C15-Al2Ca	0	DFT	WIEN2k	Al–Ca	[1] Ozturk 2005	Table IV, p. 5, row 12 report
-32.048 kJ/mol-atom	C15-Al2Ca	0	DFT	thermodynamic evaluation	Al–Ca	[1] Ozturk 2005	Table IV, p. 5, row 18 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 Al2Ca
Value	Unit	Printed	Reading	Method (class, basis)	Effective
-34.3	kJ/mol-atom	3.5	5.000e-5	4.1 (experimental_unspecified, cleaned_below_threshold)	4.1
-34.3	kJ/mol-atom	3.5	0.05	4.6 (emf, cleaned_below_threshold)	4.6
-33.4	kJ/mol-atom	0.6	5.000e-5	4.1 (experimental_unspecified, cleaned_below_threshold)	4.1
-33.4	kJ/mol-atom	0.6	0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-31.3	kJ/mol-atom	0.5	5.000e-5	4.1 (experimental_unspecified, cleaned_below_threshold)	4.1
-31.28	kJ/mol-atom	0.46	0.005	4.1 (experimental_unspecified, cleaned_below_threshold)	4.1
-29.4	kJ/mol-atom	0.9	5.000e-5	4.1 (experimental_unspecified, cleaned_below_threshold)	4.1
-29.4	kJ/mol-atom	0.9	0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-41.732	kJ/mol-atom		5.000e-5	3.9 (model_calculated, calibrated)	3.9
-32.185	kJ/mol-atom		5.000e-5	3.9 (model_calculated, calibrated)	3.9
-29.7	kJ/mol-atom		5.000e-5	3.9 (model_calculated, calibrated)	3.9
-29.7	kJ/mol-atom		0.05	3.9 (model_calculated, calibrated)	3.9
-29.28	kJ/mol-atom		0.005	3.9 (model_calculated, calibrated)	3.9
-36.604	kJ/mol-atom		5.000e-5	8.395 (dft, calibrated)	8.395
-36.272	kJ/mol-atom		5.000e-5	8.395 (dft, calibrated)	8.395
-34.018	kJ/mol-atom		5.000e-5	8.395 (dft, calibrated)	8.395
-32.136	kJ/mol-atom		5.000e-5	8.395 (dft, calibrated)	8.395
-32.048	kJ/mol-atom		5.000e-5	8.395 (dft, calibrated)	8.395

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 Al2Ca
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaaaadom	-32.104	-0.332736	Fd-3m	0	0	no
OQMD	oqmd-5774	-32.307	-0.334836	Fd-3m	0	0	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

Koray Ozturk, Yu Zhong, Long-Qing Chen, Zi-Kui Liu, Jorge O. Sofo, C. Wolverton, Linking first-principles energetics to CALPHAD: An application to thermodynamic modeling of the Al-Ca binary system, Metall Mater Trans A 36, 5-13 (2005). doi:10.1007/s11661-005-0133-0
F. ISLAM, M. MEDRAJ, THERMODYNAMIC MODELLING OF THE Mg-Al-Ca SYSTEM, Canadian Metallurgical Quarterly 44, 523-536 (2005). doi:10.1179/cmq.2005.44.4.523

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}
}