Ca2Si: enthalpy of formation

13 accepted literature formation-enthalpy value(s) (experimental 7, model 5, unspecified 1); experimental median -71.4 kJ/mol-atom (n = 5); Materials Project -41.918 kJ/mol-atom (mp-aaaaadsv); OQMD -45.505 kJ/mol-atom (oqmd-4796).

Systems: Ca–Si

Literature values

Enthalpy of formation of Ca2Si reported in the literature (13)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-483 kJ/mol (basis unstated)	Ca2Si	298.15	experimental	calorimetry	Ca–Si	[1] Anglezio 1994 cites ref. 62Shc	Table III, p. 12, row 1 report
-254.352 kJ/mol (basis unstated)	Ca2Si	298.15	experimental	effusion method	Ca–Si	[1] Anglezio 1994 cites ref. 67Mur	Table III, p. 12, row 3 report
-254.35 kJ/mol-atom	Ca2Si	298.15	experimental	Effusion	Ca–Si	[2] Gröbner 2003 cites Zviadadze 2003	Table 1, p. 2, row 4 report
-209 kJ/mol-atom	Ca2Si	298.15	experimental		Ca–Si	[2] Gröbner 2003 cites Muradov 1967	Table 1, p. 2, row 6 report
-71.4 kJ/mol-atom	Ca2Si	298.15	experimental	Calorimetry at 940K	Ca–Si	[2] Gröbner 2003 cites Wynnyckyj 1972	Table 1, p. 2, row 1 report
-56.1 kJ/mol-atom	Ca2Si	298.15	experimental	Knudsen cell	Ca–Si	[2] Gröbner 2003 cites Sudatsova 1988	Table 1, p. 2, row 10 report
-48.3 kJ/mol-atom	Ca2Si	298.15	experimental	Calorimetry	Ca–Si	[2] Gröbner 2003 cites Kubaschewski 1949	Table 1, p. 2, row 2 report
-209 kJ/mol-atom	Ca2Si	298.15	model	Calphad	Ca–Si	[2] Gröbner 2003 cites Anglezio 1994 doi	Table 1, p. 2, row 9 report
-209 kJ/mol (basis unstated)	Ca2Si		model		Ca–Si	[1] Anglezio 1994	Table III, p. 12, row 8 report
-56.1 kJ/mol-atom	Ca2Si	298.15	model	Calphad	Ca–Si	[2] Gröbner 2003	Table 1, p. 2, row 11 report
-23.864 kJ/mol (basis unstated)	Ca2Si		model	phase diagram analysis	Ca–Si	[1] Anglezio 1994 cites ref. 86Lee	Table III, p. 12, row 7 report
-23.86 kJ/mol-atom	Ca2Si	298.15	model	Calphad	Ca–Si	[2] Gröbner 2003 cites Lee 1986	Table 1, p. 2, row 8 report
-209 kJ/mol (basis unstated)	Ca2Si		unspecified		Ca–Si	[1] Anglezio 1994 cites ref. 82Wag	Table III, p. 12, row 5 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 Ca2Si
Value	Unit	Reading	Method (class, basis)	Effective
-483	kJ/mol (basis unstated)	5.000e-4	9.6 (solution_reaction_calorimetry, calibrated)	9.6
-254.352	kJ/mol (basis unstated)	5.000e-4	12.6 (kems_vapour, calibrated)	12.6
-254.35	kJ/mol-atom	0.005	4.2 (kems_vapour, calibrated)	4.2
-209	kJ/mol-atom	0.05	3.5 (unknown, calibrated)	3.5
-71.4	kJ/mol-atom	0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-56.1	kJ/mol-atom	0.05	4.2 (kems_vapour, calibrated)	4.2
-48.3	kJ/mol-atom	0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-209	kJ/mol-atom	0.05	3.9 (model_calculated, calibrated)	3.9
-209	kJ/mol (basis unstated)	5.000e-4	11.7 (model_calculated, calibrated)	11.7
-56.1	kJ/mol-atom	0.05	3.9 (model_calculated, calibrated)	3.9
-23.864	kJ/mol (basis unstated)	5.000e-4	11.7 (model_calculated, calibrated)	11.7
-23.86	kJ/mol-atom	0.005	3.9 (model_calculated, calibrated)	3.9
-209	kJ/mol (basis unstated)	5.000e-4	10.5 (unknown, calibrated)	10.5

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 Ca2Si
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaaaadsv	-41.918	-0.434447	Pnma	0	0	no
OQMD	oqmd-4796	-45.505	-0.471632	Pnma	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

J.C. Anglezio, C. Servant, I. Ansara, Contribution to the experimental and thermodynamic assessment of the AlCaFeSi system—I. AlCaFe, AlCaSi, AlFeSi and CaFeSi systems, Calphad 18, 273-309 (1994). doi:10.1016/0364-5916(94)90034-5
Joachim Gröbner, Igor Chumak, Rainer Schmid-Fetzer, Experimental study of ternary Ca–Mg–Si phase equilibria and thermodynamic assessment of Ca–Si and Ca–Mg–Si systems, Intermetallics 11, 1065-1074 (2003). doi:10.1016/j.intermet.2003.07.001

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}
}