# Ta system

> Ta system: 51 accepted literature values (crystal structure 28, formation 15, other property 6, activity / EMF / Gibbs energy 2) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

HTML: https://data.orchid-project.org/systems/TA.html · Markdown: https://data.orchid-project.org/systems/TA.md

51 accepted literature values from 10 paper(s) (experimental 10, model 3, DFT 33, unspecified 5); 0 calculated phase diagram(s).

Data: [JSON](https://data.orchid-project.org/literature/systems/TA.json) · [CSV](https://data.orchid-project.org/systems/TA.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#TA) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/TA.html) · [Markdown](https://data.orchid-project.org/systems/TA.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 10 |
| model | 3 |
| DFT | 33 |
| unspecified | 5 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| formation | 15 |
| activity / EMF / Gibbs energy | 2 |
| crystal structure | 28 |
| other property | 6 |

## Formation enthalpies

Literature values in kJ/mol-atom where the per-atom basis is known. DFT columns: the lowest-energy entry at the same composition (Materials Project 2026.04.13, OQMD v1.8; different energy references, never averaged), from [dft_parity.json](https://data.orchid-project.org/literature/dft_parity.json).

Table: Enthalpies of formation, Ta system (15)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| A15 |  | 3.0195 kJ/mol (basis unstated) | 0 | DFT |  |  | [1] Wang 2019 | Table 2, p. 22, row 4; `ORC-FAXZ25D3ZP` |  |
| C14 |  | 9.35 kJ/mol (basis unstated) | 0 | DFT |  |  | [2] Pavlů 2009 | Table 3, p. 3, row 5; `ORC-UAKXOUMUOL` |  |
| C14 |  | 9.6703 kJ/mol (basis unstated) | 0 | DFT |  |  | [1] Wang 2019 | Table 2, p. 22, row 12; `ORC-HHQPTEKF6U` |  |
| C14 |  | 9.7 kJ/mol (basis unstated) | 0 | DFT |  |  | [2] Pavlů 2009; _cites Sluiter 2006_ [doi](https://doi.org/10.1016/j.calphad.2006.09.002) | Table 3, p. 3, row 6; `ORC-D32WQJRXTD` |  |
| C15 |  | 10.94 kJ/mol (basis unstated) | 0 | DFT |  |  | [2] Pavlů 2009 | Table 3, p. 3, row 11; `ORC-RAXXYU6PRE` |  |
| C15 |  | 11.1655 kJ/mol (basis unstated) | 0 | DFT |  |  | [1] Wang 2019 | Table 2, p. 22, row 16; `ORC-BCYU4AIJ7K` |  |
| C15 |  | 11.2 kJ/mol (basis unstated) | 0 | DFT |  |  | [2] Pavlů 2009; _cites Sluiter 2006_ [doi](https://doi.org/10.1016/j.calphad.2006.09.002) | Table 3, p. 3, row 12; `ORC-JTFLOG5AAD` |  |
| C16 |  | 48.1965 kJ/mol (basis unstated) | 0 | DFT |  |  | [1] Wang 2019 | Table 2, p. 22, row 20; `ORC-EWGKEC5BSC` |  |
| C36 |  | 10.15 kJ/mol (basis unstated) | 0 | DFT |  |  | [2] Pavlů 2009 | Table 3, p. 3, row 15; `ORC-J5F2TMPJDX` |  |
| FCC |  | 23.3493 kJ/mol (basis unstated) | 0 | DFT |  |  | [1] Wang 2019 | Table 3, p. 27, row 10; `ORC-QST3H636V2` |  |
| HCP |  | 26.9804 kJ/mol (basis unstated) | 0 | DFT |  |  | [1] Wang 2019 | Table 3, p. 27, row 15; `ORC-QUYI7AWZWR` |  |
| Ta |  | 0 kJ/mol (basis unstated) | 298.15 | experimental |  |  | [3] Witusiewicz 2011 | Table 4, p. 10, row 8; `ORC-4BSOU4T3BM.e8599c` |  |
| Ta |  | 0 kJ/mol-atom |  | DFT |  |  | [4] Zhou 2009 | Table 6, p. 7, row 6; `ORC-B5SO5YS473` |  |
| Ta |  | 26.23 kJ/mol-atom |  | DFT |  |  | [4] Zhou 2009 | Table 6, p. 7, row 5; `ORC-JGKUD3RHGN` |  |
| Ta13 |  | 10.71 kJ/mol-atom | 0 | DFT |  |  | [5] Rajkumar 2015 | Table 9, p. 6, row 8; `ORC-VPO6TJUC6Z` |  |

## Other properties

### Activity / EMF / Gibbs energy (2)

Table: Activity / EMF / Gibbs energy, Ta system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Gibbs energy; _printed: Gm(ω)-Gm(β)_ | 7795 J/mol | 0 | UNKNOWN; _alloy: Ta 1_ | model | [6] Yan 2016 | Table 4, p. 5, row 6; `ORC-JOPOITBSUY` |  |
| Gibbs energy; _printed: Gm(ω)-Gm(β)_ | 21835 J/mol | 0 | UNKNOWN; _alloy: Ta 1_ | DFT | [6] Yan 2016 | Table 4, p. 5, row 5; `ORC-P7H77KKDM6` |  |

### Crystal structure (28)

Table: Crystal structure, Ta system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Lattice a | 5.45 Å | 0 | C14; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 3; `ORC-4XXYGUIOLZ.9a705d` |  |
| Lattice a | 7.65 Å | 0 | C15; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 12; `ORC-5I6LGBCPA4.0beb7e` |  |
| Lattice a | 5.44 Å | 0 | C36; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 21; `ORC-BVGRL3EJF7.e7eac8` |  |
| Lattice a | 3.31 Å |  | Nonmagnetic BCC Ta; _alloy: Ta 1_ | unspecified | [2] Pavlů 2009 | Table 1, p. 3, row 5; `ORC-R2GMWHBQ3Y` |  |
| Lattice a | 3.303 Å | 298.15 | (Ta); _alloy: Ta 1_ | model | [7] Broz 2013; _cites Smith 1983_ [doi](https://doi.org/10.1007/bf02868668) | Table 1, p. 3, row 1; `ORC-OISNK5Y7LE` |  |
| Lattice a | 3.3 Å | 298.15 | Nonmagnetic BCC Ta; _alloy: Ta 1_ | experimental | [2] Pavlů 2009; _cites Villars 1991_ | Table 1, p. 3, row 6; `ORC-NLDV3GEDW2` |  |
| Lattice a | 3.328 Å | 298.15 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017 | Table 1, p. 12, row 2; `ORC-AHB4G73OHM` |  |
| Lattice a | 3.316 Å | 298.15 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017 | Table 1, p. 12, row 1; `ORC-HAZGHBKNKW` |  |
| Lattice a | 3.32 Å | 298.15 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017; _cites ref. 36_ | Table 1, p. 12, row 5; `ORC-JE4Z4B6NLA` |  |
| Lattice a | 3.33 Å | 298.15 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017 | Table 1, p. 12, row 3; `ORC-UBEULTGHHB` |  |
| Lattice a | 3.3 Å | 298.15 | bcc-Ta; _alloy: Ta 1_ | experimental | [8] Marker 2017; _cites ref. 35_ | Table 1, p. 12, row 4; `ORC-VIEQ2RPQ6H` |  |
| Lattice a | 3.3065 Å | 298.15 | β, (Ta); _alloy: Ta 1_ | model | [3] Witusiewicz 2011; _cites Massalski 1990_ | Table 1, p. 2, row 3; `ORC-BPJKJBTZDY` |  |
| Lattice a | 3.303 Å | 298.15 | β, (Ta), bcc_A2; _alloy: Ta 1_ | experimental | [9] Witusiewicz 2010; _cites 3 vols 1990_ | Table 1, p. 2, row 3; `ORC-ACT2POQVN5` |  |
| Lattice a | 3.303 Å | 300 | (Ta); _alloy: Ta 1_ | experimental | [7] Broz 2013; _cites Smith 1983_ [doi](https://doi.org/10.1007/bf02868668) | Table 1, p. 3, row 48; `ORC-P376RUWERR` |  |
| Lattice c | 8.68 Å | 0 | C14; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 3; `ORC-4XXYGUIOLZ.cec150` |  |
| Lattice c | 17.43 Å | 0 | C36; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 21; `ORC-BVGRL3EJF7.b264aa` |  |
| Molar volume; _printed: V_ | 18.241 ų/atom | 0 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017 | Table 2, p. 13, row 1; `ORC-EHW2B6OZS5.11cc87` |  |
| Molar volume; _printed: V_ | 18.313 ų/atom | 0 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017; _cites ref. 36_ | Table 2, p. 13, row 3; `ORC-H3CXC36SUB.40916f` |  |
| Molar volume; _printed: V_ | 17.9685 ų/atom |  | bcc-Ta; _alloy: Ta 1_ | experimental | [8] Marker 2017; _cites ref. 35_ | Table 2, p. 13, row 2; `ORC-JHB5YWPEUJ.19ee9e` |  |
| lattice 2v atom | 3.724 10^7 pm^3 | 0 | C36; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 21; `ORC-BVGRL3EJF7.54b710` |  |
| lattice unspecified axis; _printed: Lattice constant_ | 3.3031 Å |  | Pure Ta; _alloy: Ta 1_ | experimental | [10] Turchi 2005 | Table I, p. 5, row 1; `ORC-2KOZ7PZT7Q` |  |
| lattice unspecified axis; _printed: Lattice constant_ | 3.2766 Å |  | Pure Ta; _alloy: Ta 1_ | unspecified | [10] Turchi 2005 | Table I, p. 5, row 8; `ORC-LBWJRR2ZOK` |  |
| lattice unspecified axis; _printed: Lattice constant_ | 3.3098 Å |  | Pure Ta; _alloy: Ta 1_ | unspecified | [10] Turchi 2005 | Table I, p. 5, row 4; `ORC-VVAJHXFBIL` |  |
| lattice v atom | 1.861 10^7 pm^3 | 0 | C14; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 3; `ORC-4XXYGUIOLZ.94268f` |  |
| lattice v atom | 1.862 10^7 pm^3 | 0 | C15; _alloy: Ta 1_ | DFT | [2] Pavlů 2009 | Table 2, p. 3, row 12; `ORC-5I6LGBCPA4.4bf712` |  |
| volume; _printed: V_ | 18.241 Å3/atom | 0 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017 | Table 2, p. 13, row 1; `ORC-EHW2B6OZS5.ed3191` |  |
| volume; _printed: V_ | 18.313 Å3/atom | 0 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017; _cites ref. 36_ | Table 2, p. 13, row 3; `ORC-H3CXC36SUB.d206de` |  |
| volume; _printed: V_ | 17.9685 Å3/atom |  | bcc-Ta; _alloy: Ta 1_ | experimental | [8] Marker 2017; _cites ref. 35_ | Table 2, p. 13, row 2; `ORC-JHB5YWPEUJ.5e269d` |  |

### Other property (6)

Table: Other property, Ta system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| bulk modulus; _printed: Bulk modulus_ | 196.1 GPa |  | Pure Ta; _alloy: Ta 1_ | experimental | [10] Turchi 2005 | Table I, p. 5, row 1; `ORC-3ISIFSJV7L` |  |
| bulk modulus; _printed: Bulk modulus_ | 206.4 GPa |  | Pure Ta; _alloy: Ta 1_ | unspecified | [10] Turchi 2005 | Table I, p. 5, row 4; `ORC-RT3JOYBTI5` |  |
| bulk modulus; _printed: Bulk modulus_ | 215.3 GPa |  | Pure Ta; _alloy: Ta 1_ | unspecified | [10] Turchi 2005 | Table I, p. 5, row 8; `ORC-WECWOFTM7S` |  |
| bulk modulus; _printed: B_ | 193.7 GPa | 0 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017 | Table 2, p. 13, row 1; `ORC-EHW2B6OZS5.4f0a5d` |  |
| bulk modulus; _printed: B_ | 195.3 GPa | 0 | bcc-Ta; _alloy: Ta 1_ | DFT | [8] Marker 2017; _cites ref. 36_ | Table 2, p. 13, row 3; `ORC-H3CXC36SUB.68956d` |  |
| bulk modulus; _printed: B_ | 200 GPa |  | bcc-Ta; _alloy: Ta 1_ | experimental | [8] Marker 2017; _cites ref. 35_ | Table 2, p. 13, row 2; `ORC-JHB5YWPEUJ.8a227e` |  |

## Sources

Reporting papers the values were read from (a value cited from another work names that work in its row).

1. Peisheng Wang, Jörg Koßmann, Ursula R. Kattner, Mauro Palumbo, Thomas Hammerschmidt, Gregory B. Olson, Thermodynamic assessment of the Co-Ta system, Calphad 64, 205-212 (2019). [doi:10.1016/j.calphad.2018.12.002](https://doi.org/10.1016/j.calphad.2018.12.002)
2. J. Pavlů, J. Vřešt’ál, M. Šob, Re-modeling of Laves phases in the Cr–Nb and Cr–Ta systems using first-principles results, Calphad 33, 179-186 (2009). [doi:10.1016/j.calphad.2008.04.006](https://doi.org/10.1016/j.calphad.2008.04.006)
3. V.T. Witusiewicz, A.A. Bondar, U. Hecht, V.M. Voblikov, O.S. Fomichov, V.M. Petyukh et al., Experimental study and thermodynamic re-assessment of the binary Fe–Ta system, Intermetallics 19, 1059-1075 (2011). [doi:10.1016/j.intermet.2011.03.018](https://doi.org/10.1016/j.intermet.2011.03.018)
4. S.H. Zhou, Y. Wang, L.-Q. Chen, Z.-K. Liu, R.E. Napolitano, Solution-based thermodynamic modeling of the Ni–Ta and Ni–Mo–Ta systems using first-principle calculations, Calphad 33, 631-641 (2009). [doi:10.1016/j.calphad.2009.06.006](https://doi.org/10.1016/j.calphad.2009.06.006)
5. V.B. Rajkumar, K.C. Hari Kumar, Gibbs energy modeling of Fe–Ta system by Calphad method assisted by experiments and ab initio calculations, Calphad 48, 157-165 (2015). [doi:10.1016/j.calphad.2014.12.006](https://doi.org/10.1016/j.calphad.2014.12.006)
6. Jia-Yi Yan, G.B. Olson, Computational thermodynamics and kinetics of displacive transformations in titanium-based alloys, Journal of Alloys and Compounds 673, 441-454 (2016). [doi:10.1016/j.jallcom.2016.02.251](https://doi.org/10.1016/j.jallcom.2016.02.251)
7. P. Broz, A.U. Khan, H. Niu, X.-Q. Chen, D. Li, J. Vrestal et al., The system Ta–V–Si: Thermodynamic modeling, Journal of Solid State Chemistry 199, 171-180 (2013). [doi:10.1016/j.jssc.2012.12.003](https://doi.org/10.1016/j.jssc.2012.12.003)
8. Cassie Marker, ShunLi Shang, Xuan L. Liu, Greta Lindwall, Zi-Kui Liu, First-principles calculations and thermodynamic modeling of the Sn-Ta system, Calphad 57, 46-54 (2017). [doi:10.1016/j.calphad.2017.03.001](https://doi.org/10.1016/j.calphad.2017.03.001)
9. V.T. Witusiewicz, A.A. Bondar, U. Hecht, J. Zollinger, V.M. Petyukh, O.S. Fomichov et al., Experimental study and thermodynamic re-assessment of the binary Al–Ta system, Intermetallics 18, 92-106 (2010). [doi:10.1016/j.intermet.2009.06.015](https://doi.org/10.1016/j.intermet.2009.06.015)
10. P. E. A. Turchi, V. Drchal, J. Kudrnovský, C. Colinet, Larry Kaufman, Zi-Kui Liu, Application of\<i>ab initio\</i>and CALPHAD thermodynamics to Mo-Ta-W alloys, Phys. Rev. B 71 (2005). [doi:10.1103/physrevb.71.094206](https://doi.org/10.1103/physrevb.71.094206)

## 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 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); 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; 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).

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_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/).