# Al2Ca: enthalpy of formation > Enthalpy of formation of Al2Ca: 18 literature value(s) with sources, pages and quotes and DFT values (Materials Project / OQMD), from ORCHID. HTML: https://data.orchid-project.org/compounds/Al2Ca.html · Markdown: https://data.orchid-project.org/compounds/Al2Ca.md 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](https://data.orchid-project.org/systems/AL-CA.html) ## Literature values Table: Enthalpy of formation of Al2Ca reported in the literature (18) | Value | Phase as printed | T (K) | Class | Method | System | Source | Location | Quote | |---:|---|---:|---|---|---|---|---|---| | -34.3 kJ/mol-atom ± 3.5 | C15-Al2Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Notin 1982_ [doi](https://doi.org/10.1016/0364-5916%2882%2990015-3) | Table IV, p. 5, row 21; `ORC-6WOBDFQDT6.aa92cb` | | | -34.3 kJ/mol-atom ± 3.5 | Al2Ca | 800 | experimental | Emf | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] ISLAM 2005; _cites ref. 35_ | Table V, p. 9, row 3; `ORC-EVWHCHSGOM.95afda` | | | -33.4 kJ/mol-atom ± 0.6 | C15-Al2Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Notin 1995_ [doi](https://doi.org/10.1016/0925-8388%2894%2906001-0) | Table IV, p. 5, row 20; `ORC-7WTP4LTZGH.dc5f91` | | | -33.4 kJ/mol-atom ± 0.6 | Al2Ca | 1038 | experimental | Precipitation Calorimetry | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] ISLAM 2005; _cites ref. 31_ | Table V, p. 9, row 2; `ORC-VM6THGCH2Z` | | | -31.3 kJ/mol-atom ± 0.5 | C15-Al2Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Veleckis 1981_ [doi](https://doi.org/10.1016/0022-5088%2881%2990098-9) | Table IV, p. 5, row 22; `ORC-FHBP4YQMQO.3fd5f4` | | | -31.28 kJ/mol-atom ± 0.46 | Al2Ca | 788 | experimental | Hydrogen Titration | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] ISLAM 2005; _cites ref. 34_ | Table V, p. 9, row 1; `ORC-4VF2YU5IU5.e8975a` | | | -29.4 kJ/mol-atom ± 0.9 | C15-Al2Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Kevorkov 2001_ | Table IV, p. 5, row 19; `ORC-TCPC77DHKK.452f64` | | | -29.4 kJ/mol-atom ± 0.9 | Al2Ca | 298.15 | experimental | Dissolution Calorimetry | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] ISLAM 2005; _cites ref. 26_ | Table V, p. 9, row 4; `ORC-UTECLILISV` | | | -41.732 kJ/mol-atom | C15-Al2Ca | | model | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Itkin 1988_ [doi](https://doi.org/10.1007/bf02883160) | Table IV, p. 5, row 15; `ORC-KZBC6CU7AU.9f5935` | | | -32.185 kJ/mol-atom | C15-Al2Ca | | model | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Ozturk 2002_ [doi](https://doi.org/10.1016/s0925-8388%2801%2901713-3) | Table IV, p. 5, row 16; `ORC-DJCUAWX7H7.cca9eb` | | | -29.7 kJ/mol-atom | C15-Al2Ca | | model | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005; _cites Kevorkov 2001_ | Table IV, p. 5, row 17; `ORC-GBNRGRM26L.98ea11` | | | -29.7 kJ/mol-atom | Al2Ca | 800 | model | Assessed | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] ISLAM 2005; _cites ref. 26_ | Table V, p. 9, row 5; `ORC-UW6X4DZ2U2.ada1d7` | | | -29.28 kJ/mol-atom | Al2Ca | 298.15 | model | Calculated in this work | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] ISLAM 2005 | Table V, p. 9, row 6; `ORC-SNUCDIATXV.ffb8e2` | | | -36.604 kJ/mol-atom | C15-Al2Ca | 0 | DFT | WIEN2k | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005 | Table IV, p. 5, row 11; `ORC-BIBOWE6FPC.9d438f` | | | -36.272 kJ/mol-atom | C15-Al2Ca | 0 | DFT | VASP | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005 | Table IV, p. 5, row 13; `ORC-AJBLYDVVJ7.a01f20` | | | -34.018 kJ/mol-atom | C15-Al2Ca | 0 | DFT | VASP | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005 | Table IV, p. 5, row 14; `ORC-WAZ6UJADGF.8da616` | | | -32.136 kJ/mol-atom | C15-Al2Ca | 0 | DFT | WIEN2k | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005 | Table IV, p. 5, row 12; `ORC-RRTXNAEBFG.4b59a8` | | | -32.048 kJ/mol-atom | C15-Al2Ca | 0 | DFT | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Ozturk 2005 | Table IV, p. 5, row 18; `ORC-HH5P332BD5.027576` | | ### Uncertainty budget Components kept separate, in the value's unit (literature [SCHEMA.md](https://data.orchid-project.org/literature/SCHEMA.md), [UNCERTAINTY_CALIBRATION.md](https://data.orchid-project.org/literature/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. Table: Uncertainty budget of the literature values of Al2Ca | Value | Unit | Printed | Reading | Method (class, basis) | Composition | Scatter | Conversion | 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. Table: 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](https://doi.org/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](https://doi.org/10.1007/s11837-013-0755-4) (CC BY 4.0); ## Sources 1. 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](https://doi.org/10.1007/s11661-005-0133-0) 2. 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](https://doi.org/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). https://doi.org/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). https://doi.org/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). https://doi.org/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. ```bibtex @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} } ``` --- Derived data CC BY 4.0 ([licence](https://creativecommons.org/licenses/by/4.0/)): cite ORCHID ([CITATION.cff](https://data.orchid-project.org/CITATION.cff)) and the original sources. Quotes are short excerpts kept so that each value can be checked; they remain under the publishers' copyright and are not relicensed. Source papers, page images and full text are not redistributed. Field reference: [SCHEMA.md](https://data.orchid-project.org/literature/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt). Found an error? The report link of a value (Markdown: its id, ORC-..., in the Location column) opens a pre-filled GitHub issue, https://github.com/orchid-calphad/orchid-data/issues/new?template=report-value-error.yml&record_id=\, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).