# Ca2Si: enthalpy of formation

> Enthalpy of formation of Ca2Si: 13 literature value(s) with sources, pages and quotes and DFT values (Materials Project / OQMD), from ORCHID.

HTML: https://data.orchid-project.org/compounds/Ca2Si.html · Markdown: https://data.orchid-project.org/compounds/Ca2Si.md

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](https://data.orchid-project.org/systems/CA-SI.html)

## Literature values

Table: Enthalpy of formation of Ca2Si reported in the literature (13)

| Value | Phase as printed | T (K) | Class | Method | System | Source | Location | Quote |
|---:|---|---:|---|---|---|---|---|---|
| -483 kJ/mol (basis unstated) | Ca2Si | 298.15 | experimental | calorimetry | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [1] Anglezio 1994; _cites ref. 62Shc_ | Table III, p. 12, row 1; `ORC-4PJ5LDNA3U` |  |
| -254.352 kJ/mol (basis unstated) | Ca2Si | 298.15 | experimental | effusion method | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [1] Anglezio 1994; _cites ref. 67Mur_ | Table III, p. 12, row 3; `ORC-JZPRQCK6LV.6f5dfd` |  |
| -254.35 kJ/mol-atom | Ca2Si | 298.15 | experimental | Effusion | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Zviadadze 2003_ | Table 1, p. 2, row 4; `ORC-5UBITMWKOB.6652b8` |  |
| -209 kJ/mol-atom | Ca2Si | 298.15 | experimental |  | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Muradov 1967_ | Table 1, p. 2, row 6; `ORC-4M4CL2ZEFR.f6076c` |  |
| -71.4 kJ/mol-atom | Ca2Si | 298.15 | experimental | Calorimetry at 940K | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Wynnyckyj 1972_ | Table 1, p. 2, row 1; `ORC-F6T2FC7SLV.bfb311` |  |
| -56.1 kJ/mol-atom | Ca2Si | 298.15 | experimental | Knudsen cell | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Sudatsova 1988_ | Table 1, p. 2, row 10; `ORC-6N2AN7HUCW.666538` |  |
| -48.3 kJ/mol-atom | Ca2Si | 298.15 | experimental | Calorimetry | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Kubaschewski 1949_ | Table 1, p. 2, row 2; `ORC-VOQICLLMUA` |  |
| -209 kJ/mol-atom | Ca2Si | 298.15 | model | Calphad | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Anglezio 1994_ [doi](https://doi.org/10.1016/0364-5916%2894%2990034-5) | Table 1, p. 2, row 9; `ORC-DSIDS2MAX2.9b2cda` |  |
| -209 kJ/mol (basis unstated) | Ca2Si |  | model |  | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [1] Anglezio 1994 | Table III, p. 12, row 8; `ORC-SGG43HL74Z.f8ca49` |  |
| -56.1 kJ/mol-atom | Ca2Si | 298.15 | model | Calphad | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003 | Table 1, p. 2, row 11; `ORC-O66YRHEN77.ed824e` |  |
| -23.864 kJ/mol (basis unstated) | Ca2Si |  | model | phase diagram analysis | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [1] Anglezio 1994; _cites ref. 86Lee_ | Table III, p. 12, row 7; `ORC-G3QGQT2UTI.90da11` |  |
| -23.86 kJ/mol-atom | Ca2Si | 298.15 | model | Calphad | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [2] Gröbner 2003; _cites Lee 1986_ | Table 1, p. 2, row 8; `ORC-3HYDEZEJHJ.c9f16c` |  |
| -209 kJ/mol (basis unstated) | Ca2Si |  | unspecified |  | [Ca–Si](https://data.orchid-project.org/systems/CA-SI.html) | [1] Anglezio 1994; _cites ref. 82Wag_ | Table III, p. 12, row 5; `ORC-NHL3WKUEZI.ecff0a` |  |

### 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 Ca2Si

| Value | Unit | Printed | Reading | Method (class, basis) | Composition | Scatter | Conversion | 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.

Table: 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](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. 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](https://doi.org/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). 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/).