# C–Nb system

> C–Nb system: 56 accepted literature values (invariant reaction 25, heat capacity / entropy / enthalpy 16, crystal structure 10, formation 3) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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

56 accepted literature values from 2 paper(s) (experimental 30, model 13, DFT 13); 0 calculated phase diagram(s). 5 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: [JSON](https://data.orchid-project.org/literature/systems/C-NB.json) · [CSV](https://data.orchid-project.org/systems/C-NB.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#C-NB) · [phases (6)](https://data.orchid-project.org/phases/pages/C-NB.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/C-NB.html) · [Markdown](https://data.orchid-project.org/systems/C-NB.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 30 |
| model | 13 |
| DFT | 13 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 25 |
| phase transition | 2 |
| formation | 3 |
| heat capacity / entropy / enthalpy | 16 |
| crystal structure | 10 |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/C/C-NB.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/C/C-NB.json) · [CALPHAD hull NbC-01Lee](https://data.orchid-project.org/hulls/calphad-sgte/C/C-NB--NbC-01Lee.json) · [CALPHAD hull NbC-13Khv](https://data.orchid-project.org/hulls/calphad-sgte/C/C-NB--NbC-13Khv.json) · [CALPHAD hull NbC-90Hua](https://data.orchid-project.org/hulls/calphad-sgte/C/C-NB--NbC-90Hua.json) · [CALPHAD hull NbC-97Hua-LB](https://data.orchid-project.org/hulls/calphad-sgte/C/C-NB--NbC-97Hua-LB.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the C–Nb system (25)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 3886 | congruent melting: NbC = Liquid | NbC: C 0.45 | model | [1] Huang 1990 | Table 1, p. 3, row 18; `ORC-CN2RJSL4BH` |  |
| 3886 | congruent melting: NbC = Liquid | NbC: C 0.44 | experimental | [1] Huang 1990; _cites RUDY 1968_ | Table 1, p. 3, row 17; `ORC-LVJN437WBA` |  |
| 3873 | congruent melting: NbC = Liquid | NbC: C 0.5 | experimental | [1] Huang 1990; _cites KIMURA 1961_ | Table 1, p. 3, row 16; `ORC-TONSC272M2` |  |
| 3773 | congruent melting: NbC = Liquid | NbC: C 0.46 | experimental | [1] Huang 1990; _cites STORMS 1960_ | Table 1, p. 3, row 14; `ORC-Q2ZQSSVWEI` |  |
| 3753 | congruent melting: NbC = Liquid | NbC: C 0.5, Nb 0.5; Liquid: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites NADLER 1960_ | Table 1, p. 3, row 15; `ORC-EWHVFPAOIU` |  |
| 3673 | Liquid = NbC + graphite | NbC: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites STORMS 1960_ | Table 1, p. 3, row 19; `ORC-BWSP6VSRP3` |  |
| 3578 | Liquid = NbC + graphite | Liquid: C 0.6; NbC: C 0.49 | experimental | [1] Huang 1990; _cites RUDY 1968_ | Table 1, p. 3, row 23; `ORC-QBE4TG4CW7` |  |
| 3573 | Liquid = NbC + graphite | Liquid: C 0.6; NbC: C 0.49 | model | [1] Huang 1990 | Table 1, p. 3, row 24; `ORC-JQKELCFWFN` |  |
| 3573 | Liquid = NbC + graphite | Liquid: C 0.605; NbC: C 0.5 | experimental | [1] Huang 1990; _cites KIMURA 1961_ | Table 1, p. 3, row 21; `ORC-XZFTE7TSR4` |  |
| 3493 | Liquid = NbC + graphite | NbC: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites NADLER 1960_ | Table 1, p. 3, row 20; `ORC-4IHEO5IMWS` |  |
| 3493 | Liquid = NbC + graphite | NbC: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites ADELSBERG 1966_ | Table 1, p. 3, row 22; `ORC-XPE2AQZBKT` |  |
| 3363 | Nb2C = Liquid + NbC | Nb2C: C 0.333; Liquid: C 0.32; NbC: C 0.36 | experimental | [1] Huang 1990; _cites STORMS 1960_ | Table 1, p. 3, row 7; `ORC-ULQ3QYFSR7` |  |
| 3353 | Nb2C = Liquid + NbC | Nb2C: C 0.333333, Nb 0.666667; NbC: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites NADLER 1960_ | Table 1, p. 3, row 8; `ORC-D76Y7BPTG2` |  |
| 3353 | Nb2C = Liquid + NbC | Nb2C: C 0.333; Liquid: C 0.3; NbC: C 0.36 | experimental | [1] Huang 1990; _cites KIMURA 1961_ | Table 1, p. 3, row 9; `ORC-GSHRJA4VJK` |  |
| 3308 | Nb2C = Liquid + NbC | Nb2C: C 0.345; Liquid: C 0.3; NbC: C 0.37 | experimental | [1] Huang 1990; _cites RUDY 1968_ | Table 1, p. 3, row 10; `ORC-YT5AFOUMBL` |  |
| 2800 | Nb2C = Liquid + NbC | Nb2C: C 0.333333, Nb 0.666667; NbC: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites w 1972_ | Table 1, p. 3, row 12; `ORC-5QSAHIYTY7` |  |
| 2800 | Nb2C = Liquid + NbC | Nb2C: C 0.333333, Nb 0.666667; NbC: C 0.5, Nb 0.5 | experimental | [1] Huang 1990; _cites STORMS 1990_ | Table 1, p. 3, row 11; `ORC-GRRBOBRR3W` |  |
| 2800 | Nb2C = Liquid + NbC | Nb2C: C 0.29; Liquid: C 0.15; NbC: C 0.29 | model | [1] Huang 1990 | Table 1, p. 3, row 13; `ORC-QOMDVHY7FA` |  |
| 2799 | metatectic/catatectic: L-NbC-Nb2C |  | model | [1] Huang 1990 | p. 4; `ORC-PR3TDQUFHC` | “The calculated three phase equilibrium L-NbC-Nb2C at 2799 K is metatectic instead of the typical peritectic equilibrium, as reported in most experimental work.” |
| 2613 | Liquid = bcc + Nb2C | Liquid: C 0.135; bcc: C 0.06; Nb2C: C 0.28 | experimental | [1] Huang 1990; _cites KIMURA 1961_ | Table 1, p. 3, row 3; `ORC-M5QHB56AQC` |  |
| 2608 | Liquid = bcc + Nb2C | Liquid: C 0.105; bcc: C 0.06; Nb2C: C 0.28 | experimental | [1] Huang 1990; _cites STORMS 1960_ | Table 1, p. 3, row 1; `ORC-7OBMJEOPLN` |  |
| 2608 | Liquid = bcc + Nb2C | Liquid: C 0.105; bcc: C 0.075; Nb2C: C 0.28 | experimental | [1] Huang 1990; _cites RUDY 1968_ | Table 1, p. 3, row 5; `ORC-AWHMW45J2T` |  |
| 2608 | Liquid = bcc + Nb2C | Liquid: C 0.105; bcc: C 0.053; Nb2C: C 0.28 | model | [1] Huang 1990 | Table 1, p. 3, row 6; `ORC-B56UJ35RXO` |  |
| 2601 | Liquid = bcc + Nb2C | Nb2C: C 0.333333, Nb 0.666667 | experimental | [1] Huang 1990; _cites NADLER 1960_ | Table 1, p. 3, row 2; `ORC-EATQ2O737H` |  |
| 2503 | Liquid = bcc + Nb2C | Liquid: C 0.105; bcc: C 0.06; Nb2C: C 0.31 | experimental | [1] Huang 1990; _cites ELLIOTT 1961_ | Table 1, p. 3, row 4; `ORC-OA5N7QX6XM` |  |

## 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, C–Nb system (3)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Nb3C |  | 34.3728 kJ/mol-atom | 0 | DFT |  |  | [2] Khvan 2012 | Table 1, p. 4, row 1; `ORC-5P2WKOP3S6` |  |
| Nb5C2 |  | -15.8511 kJ/mol-atom | 0 | DFT |  |  | [2] Khvan 2012 | Table 1, p. 4, row 2; `ORC-YX7DW62EWY` |  |
| Nb7C3 |  | 15.1964 kJ/mol-atom | 0 | DFT |  |  | [2] Khvan 2012 | Table 1, p. 4, row 3; `ORC-BDWBO3XXDG` |  |

## Other properties

### Phase transition (2)

Table: Phase transition, C–Nb system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 2800 K | 2800 | Nb2C | experimental | [1] Huang 1990 | p. 2; `ORC-X5SHQ6UPMG.17203a` | “Nb2C decomposes close to 2800 K and NbC melts congruently at 3886 K.” |
| Phase transition | 3886 K | 3886 | congruent transformation | experimental | [1] Huang 1990 | p. 2; `ORC-X5SHQ6UPMG.09f2e2` | “Nb2C decomposes close to 2800 K and NbC melts congruently at 3886 K.” |

### Heat capacity / entropy / enthalpy (16)

Table: Heat capacity / entropy / enthalpy, C–Nb system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: °S298_ | 21.36 J/mol (basis unstated)/K | 298.15 | Nb2C; _alloy: Nb 0.666667_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 7; `ORC-CUPFIOVFWV.d173c5` |  |
| Entropy; _printed: °S298_ | 21.65 J/mol (basis unstated)/K | 298.15 | Nb2C; _alloy: Nb 0.666667_ | model | [1] Huang 1990 | Table 3, p. 8, row 8; `ORC-VCWFSAFTH6.6f4993` |  |
| Entropy; _printed: °S298_ | 20.44 J/mol (basis unstated)/K | 298.15 | NbC0.702; _alloy: Nb 0.587544_ | model | [1] Huang 1990 | Table 3, p. 8, row 6; `ORC-GFE5LUATVG.9fc773` |  |
| Entropy; _printed: °S298_ | 18.75 J/mol (basis unstated)/K | 298.15 | NbC0.702; _alloy: Nb 0.587544_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 5; `ORC-SPFN4X3KWN.6eafb1` |  |
| Entropy; _printed: °S298_ | 19.83 J/mol (basis unstated)/K | 298.15 | NbC0.825; _alloy: Nb 0.547945_ | model | [1] Huang 1990 | Table 3, p. 8, row 4; `ORC-AARFSZPASE.3318b4` |  |
| Entropy; _printed: °S298_ | 18.04 J/mol (basis unstated)/K | 298.15 | NbC0.825; _alloy: Nb 0.547945_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 3; `ORC-MFKK4NG7HK.92057d` |  |
| Entropy; _printed: °S298_ | 17.52 J/mol (basis unstated)/K | 298.15 | NbC0.98; _alloy: Nb 0.505051_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 1; `ORC-C6PUWCXQ26.9c2c7d` |  |
| Entropy; _printed: °S298_ | 17.45 J/mol (basis unstated)/K | 298.15 | NbC0.98; _alloy: Nb 0.505051_ | model | [1] Huang 1990 | Table 3, p. 8, row 2; `ORC-UCY5JXSD6C.094021` |  |
| Heat capacity; _printed: °Cp,298_ | 21.17 J/mol (basis unstated)/K | 298.15 | Nb2C; _alloy: Nb 0.666667_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 7; `ORC-CUPFIOVFWV.3b5274` |  |
| Heat capacity; _printed: °Cp,298_ | 20.93 J/mol (basis unstated)/K | 298.15 | Nb2C; _alloy: Nb 0.666667_ | model | [1] Huang 1990 | Table 3, p. 8, row 8; `ORC-VCWFSAFTH6.0e73a5` |  |
| Heat capacity; _printed: °Cp,298_ | 19.87 J/mol (basis unstated)/K | 298.15 | NbC0.702; _alloy: Nb 0.587544_ | model | [1] Huang 1990 | Table 3, p. 8, row 6; `ORC-GFE5LUATVG.1a1537` |  |
| Heat capacity; _printed: °Cp,298_ | 19.59 J/mol (basis unstated)/K | 298.15 | NbC0.702; _alloy: Nb 0.587544_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 5; `ORC-SPFN4X3KWN.ff2053` |  |
| Heat capacity; _printed: °Cp,298_ | 19.34 J/mol (basis unstated)/K | 298.15 | NbC0.825; _alloy: Nb 0.547945_ | model | [1] Huang 1990 | Table 3, p. 8, row 4; `ORC-AARFSZPASE.505a01` |  |
| Heat capacity; _printed: °Cp,298_ | 19.28 J/mol (basis unstated)/K | 298.15 | NbC0.825; _alloy: Nb 0.547945_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 3; `ORC-MFKK4NG7HK.f146b5` |  |
| Heat capacity; _printed: °Cp,298_ | 18.57 J/mol (basis unstated)/K | 298.15 | NbC0.98; _alloy: Nb 0.505051_ | experimental | [1] Huang 1990; _cites SANDENAW 1965_ | Table 3, p. 8, row 1; `ORC-C6PUWCXQ26.0d4942` |  |
| Heat capacity; _printed: °Cp,298_ | 18.77 J/mol (basis unstated)/K | 298.15 | NbC0.98; _alloy: Nb 0.505051_ | model | [1] Huang 1990 | Table 3, p. 8, row 2; `ORC-UCY5JXSD6C.cda623` |  |

### Crystal structure (10)

Table: Crystal structure, C–Nb system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Lattice a; _printed: a_ | 5.08 Å | 0 | Nb3C; _alloy: Nb 0.75_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 1; `ORC-NNE442LTF2.e6259b` |  |
| Lattice a; _printed: a_ | 12.66 Å | 0 | Nb5C2; _alloy: Nb 0.714286_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 2; `ORC-IONHDU43CI.fd711c` |  |
| Lattice a; _printed: a_ | 4.53 Å | 0 | Nb7C3; _alloy: Nb 0.7_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 3; `ORC-KFWBA5VF5P.7ef747` |  |
| Lattice b; _printed: b_ | 7.66 Å | 0 | Nb3C; _alloy: Nb 0.75_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 1; `ORC-NNE442LTF2.210dab` |  |
| Lattice b; _printed: b_ | 5.45 Å | 0 | Nb5C2; _alloy: Nb 0.714286_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 2; `ORC-IONHDU43CI.210458` |  |
| Lattice b; _printed: b_ | 7.92 Å | 0 | Nb7C3; _alloy: Nb 0.7_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 3; `ORC-KFWBA5VF5P.51b6f3` |  |
| Lattice c; _printed: c_ | 6.31 Å | 0 | Nb3C; _alloy: Nb 0.75_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 1; `ORC-NNE442LTF2.f2b466` |  |
| Lattice c; _printed: c_ | 5.87 Å | 0 | Nb5C2; _alloy: Nb 0.714286_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 2; `ORC-IONHDU43CI.ac4b70` |  |
| Lattice c; _printed: c_ | 15.97 Å | 0 | Nb7C3; _alloy: Nb 0.7_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 3; `ORC-KFWBA5VF5P.48fe7f` |  |
| lattice unspecified axis; _printed: β_ | 97.23 unknown | 0 | Nb5C2; _alloy: Nb 0.714286_ | DFT | [2] Khvan 2012 | Table 1, p. 4, row 2; `ORC-IONHDU43CI.8325a1` |  |

## Sources

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

1. Weiming Huang, Thermodynamic evaluation of Nb–C system, Materials Science and Technology 6, 687-694 (1990). [doi:10.1179/mst.1990.6.8.687](https://doi.org/10.1179/mst.1990.6.8.687)
2. A.V. Khvan, B. Hallstedt, K. Chang, Thermodynamic assessment of Cr–Nb–C and Mn–Nb–C systems, Calphad 39, 54-61 (2012). [doi:10.1016/j.calphad.2012.09.002](https://doi.org/10.1016/j.calphad.2012.09.002)

## 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-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD) (version 2026.10), Zenodo (2026). https://doi.org/10.5281/zenodo.23735891
- 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); 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_hulls_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD)}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735891},
  url       = {https://doi.org/10.5281/zenodo.23735891}
}

@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/).