# Al4Ca: enthalpy of formation

> Enthalpy of formation of Al4Ca: 22 literature value(s) with sources, pages and quotes and DFT values (Materials Project / OQMD), from ORCHID.

HTML: https://data.orchid-project.org/compounds/Al4Ca.html · Markdown: https://data.orchid-project.org/compounds/Al4Ca.md

22 accepted literature formation-enthalpy value(s) (experimental 11, model 7, DFT 4); experimental median -19.4 kJ/mol-atom (n = 6); Materials Project -18.794 kJ/mol-atom (mp-aaaaacph); OQMD -18.472 kJ/mol-atom (oqmd-2168879).

Systems: [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html)

## Literature values

Table: Enthalpy of formation of Al4Ca reported in the literature (22)

| Value | Phase as printed | T (K) | Class | Method | System | Source | Location | Quote |
|---:|---|---:|---|---|---|---|---|---|
| -219.5 kJ/mol (basis unstated) ± 20 | Al₄Ca | 298.15 | experimental | dissolution | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994; _cites ref. 59Koc_ | Table II, p. 8, row 2; `ORC-LXRU5OQKZV.15fe71` |  |
| -209 kJ/mol (basis unstated) ± 30 | Al₄Ca | 298.15 | experimental | combustion | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994; _cites ref. 59Koc_ | Table II, p. 8, row 1; `ORC-EJFC52C5XG.dc96fc` |  |
| -100.9 kJ/mol (basis unstated) ± 1.9 | Al₄Ca | 298.15 | experimental | H₂ titration | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994; _cites ref. 81Vel_ | Table II, p. 8, row 9; `ORC-5XLNAMXD2F.b40b90` |  |
| -97 kJ/mol (basis unstated) ± 16.5 | Al₄Ca | 800 | experimental | e.m.f | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994; _cites ref. 82Not2_ | Table II, p. 8, row 6; `ORC-JJXT5PKAWV.05737a` |  |
| -93.5 kJ/mol (basis unstated) ± 1.25 | Al₄Ca | 953 | experimental | calorimetry | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994; _cites ref. 82Not1_ | Table II, p. 8, row 5; `ORC-TSGCRXNQPF.382a6d` |  |
| -20.2 kJ/mol-atom ± 0.4 | Al4Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005; _cites Veleckis 1981_ [doi](https://doi.org/10.1016/0022-5088%2881%2990098-9) | Table IV, p. 5, row 9; `ORC-IGHKVCH3WK.e8a495` |  |
| -20.18 kJ/mol-atom ± 0.38 | Al4Ca | 788 | experimental | Hydrogen Titration | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [3] ISLAM 2005; _cites ref. 34_ | Table V, p. 9, row 7; `ORC-V6C7CC5AWB.96c99b` |  |
| -19.4 kJ/mol-atom ± 3.3 | Al4Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005; _cites Notin 1982_ [doi](https://doi.org/10.1016/0364-5916%2882%2990015-3) | Table IV, p. 5, row 10; `ORC-NEIOD6VMFX.382bad` |  |
| -19.4 kJ/mol-atom ± 3.3 | Al4Ca | 800 | experimental | Emf | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [3] ISLAM 2005; _cites ref. 35_ | Table V, p. 9, row 9; `ORC-XCFMJUUOJ7.2df71d` |  |
| -18.7 kJ/mol-atom ± 0.3 | Al4Ca | 1038 | experimental | Precipitation Calorimetry | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [3] ISLAM 2005; _cites ref. 31_ | Table V, p. 9, row 8; `ORC-6QKP4VARKE` |  |
| -18.7 kJ/mol-atom ± 0.3 | Al4Ca | 298.15 | experimental | Experiment | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005; _cites Notin 1995_ [doi](https://doi.org/10.1016/0925-8388%2894%2906001-0) | Table IV, p. 5, row 8; `ORC-PNDWNRMG4M.781315` |  |
| -100.509 kJ/mol (basis unstated) | Al₄Ca | 800 | model | optimization | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994 | Table II, p. 8, row 8; `ORC-VFOS3PDKWJ.035384` |  |
| -93.5 kJ/mol (basis unstated) | Al₄Ca |  | model | optimization | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [1] Anglezio 1994; _cites ref. 88Itk_ | Table II, p. 8, row 10; `ORC-QATZUPXM73.904686` |  |
| -28.968 kJ/mol-atom | Al4Ca |  | model | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005; _cites Itkin 1988_ [doi](https://doi.org/10.1007/bf02883160) | Table IV, p. 5, row 4; `ORC-5BNEP3SMRJ.9e2ab6` |  |
| -21 kJ/mol-atom | Al4Ca | 800 | model | Assessed | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [3] ISLAM 2005; _cites ref. 26_ | Table V, p. 9, row 10; `ORC-PM3XOMMOPJ.ef7fa2` |  |
| -21 kJ/mol-atom | Al4Ca |  | model | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005; _cites Kevorkov 2001_ | Table IV, p. 5, row 6; `ORC-Y4OP5S2EAC.694bd0` |  |
| -19.248 kJ/mol-atom | Al4Ca |  | model | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005; _cites Ozturk 2002_ [doi](https://doi.org/10.1016/s0925-8388%2801%2901713-3) | Table IV, p. 5, row 5; `ORC-YFAK27MANA.76e24e` |  |
| -17.27 kJ/mol-atom | Al4Ca | 298.15 | model | Calculated in this work | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [3] ISLAM 2005 | Table V, p. 9, row 11; `ORC-NEVTWCUSSA.579ca6` |  |
| -21.615 kJ/mol-atom | Al4Ca | 0 | DFT | VASP | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005 | Table IV, p. 5, row 3; `ORC-J5T6TBKDML.ce13f5` |  |
| -20.034 kJ/mol-atom | Al4Ca | 0 | DFT | thermodynamic evaluation | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005 | Table IV, p. 5, row 7; `ORC-ARDICSAW5Q.302cb1` |  |
| -19.56 kJ/mol-atom | Al4Ca | 0 | DFT | WIEN2k | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005 | Table IV, p. 5, row 1; `ORC-72BYE267EP.c00d79` |  |
| -19.208 kJ/mol-atom | Al4Ca | 0 | DFT | VASP | [Al–Ca](https://data.orchid-project.org/systems/AL-CA.html) | [2] Ozturk 2005 | Table IV, p. 5, row 2; `ORC-2KOSDBV2KV.80c689` |  |

### 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 Al4Ca

| Value | Unit | Printed | Reading | Method (class, basis) | Composition | Scatter | Conversion | Effective |
|---:|---|---:|---:|---|---:|---:|---:|---:|
| -219.5 | kJ/mol (basis unstated) | 20 | 5.000e-5 | 16 (solution_reaction_calorimetry, calibrated) |  |  |  | 20 |
| -209 | kJ/mol (basis unstated) | 30 | 5.000e-5 | 5 (combustion_calorimetry, cleaned_below_threshold) |  |  |  | 30 |
| -100.9 | kJ/mol (basis unstated) | 1.9 | 5.000e-5 | 20.5 (experimental_unspecified, cleaned_below_threshold) |  |  |  | 20.5 |
| -97 | kJ/mol (basis unstated) | 16.5 | 5.000e-5 | 23 (emf, cleaned_below_threshold) |  |  |  | 23 |
| -93.5 | kJ/mol (basis unstated) | 1.25 | 5.000e-5 | 16 (solution_reaction_calorimetry, calibrated) |  |  |  | 16 |
| -20.2 | kJ/mol-atom | 0.4 | 5.000e-5 | 4.1 (experimental_unspecified, cleaned_below_threshold) |  |  |  | 4.1 |
| -20.18 | kJ/mol-atom | 0.38 | 0.005 | 4.1 (experimental_unspecified, cleaned_below_threshold) |  |  |  | 4.1 |
| -19.4 | kJ/mol-atom | 3.3 | 5.000e-5 | 4.1 (experimental_unspecified, cleaned_below_threshold) |  |  |  | 4.1 |
| -19.4 | kJ/mol-atom | 3.3 | 0.05 | 4.6 (emf, cleaned_below_threshold) |  |  |  | 4.6 |
| -18.7 | kJ/mol-atom | 0.3 | 0.05 | 3.2 (solution_reaction_calorimetry, calibrated) |  |  |  | 3.2 |
| -18.7 | kJ/mol-atom | 0.3 | 5.000e-5 | 4.1 (experimental_unspecified, cleaned_below_threshold) |  |  |  | 4.1 |
| -100.509 | kJ/mol (basis unstated) |  | 5.000e-5 | 19.5 (model_calculated, calibrated) |  |  |  | 19.5 |
| -93.5 | kJ/mol (basis unstated) |  | 5.000e-5 | 19.5 (model_calculated, calibrated) |  |  |  | 19.5 |
| -28.968 | kJ/mol-atom |  | 5.000e-5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -21 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -21 | kJ/mol-atom |  | 5.000e-5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -19.248 | kJ/mol-atom |  | 5.000e-5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -17.27 | kJ/mol-atom |  | 0.005 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -21.615 | kJ/mol-atom |  | 5.000e-5 | 8.395 (dft, calibrated) |  |  |  | 8.395 |
| -20.034 | kJ/mol-atom |  | 5.000e-5 | 8.395 (dft, calibrated) |  |  |  | 8.395 |
| -19.56 | kJ/mol-atom |  | 5.000e-5 | 8.395 (dft, calibrated) |  |  |  | 8.395 |
| -19.208 | 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 Al4Ca

| Source | Entry | kJ/mol-atom | eV/atom | Space group | E above hull (kJ/mol-atom) | E above hull (eV/atom) | Theoretical |
|---|---|---:|---:|---|---:|---:|---|
| Materials Project | mp-aaaaacph | -18.794 | -0.19479 | I4/mmm | 0.4681 | 0.0049 | no |
| OQMD | oqmd-2168879 | -18.472 | -0.191446 | C2/m | 0.9123 | 0.0095 | 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](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. 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](https://doi.org/10.1016/0364-5916%2894%2990034-5)
2. 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)
3. 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=\<id>, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).