# NbSi2: enthalpy of formation

> Enthalpy of formation of NbSi2: 32 literature value(s) with sources, pages and quotes and DFT values (Materials Project / OQMD), from ORCHID.

HTML: https://data.orchid-project.org/compounds/NbSi2.html · Markdown: https://data.orchid-project.org/compounds/NbSi2.md

32 accepted literature formation-enthalpy value(s) (experimental 4, model 25, DFT 1, unspecified 2); experimental median -53.7 kJ/mol-atom (n = 4); Materials Project -48.427 kJ/mol-atom (mp-aaaaarxo); OQMD -53.121 kJ/mol-atom (oqmd-30789).

Systems: [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html)

## Literature values

Table: Enthalpy of formation of NbSi2 reported in the literature (32)

| Value | Phase as printed | T (K) | Class | Method | System | Source | Location | Quote |
|---:|---|---:|---|---|---|---|---|---|
| -53.7 kJ/mol-atom | NbSi2 | 298.15 | experimental |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [1] Fernandes 2002; _cites Meschel 1998_ [doi](https://doi.org/10.1016/s0925-8388%2898%2900504-0) | Table 3, p. 6, row 8; `ORC-25YMX5AZDL` |  |
| -53.7 kJ/mol-atom ± 1.6 | NbSi2 | 298.15 | experimental | Calorimetry | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Meschel 1998_ [doi](https://doi.org/10.1016/s0925-8388%2898%2900504-0) | Table 3, p. 6, row 15; `ORC-D2GEUAFSA3.17618f` |  |
| -53.7 kJ/mol-atom ± 1.6 | (NbSi2) | 273.15 | experimental | Calorimetry | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [3] Geng 2009; _cites Meschel 1998_ [doi](https://doi.org/10.1016/s0925-8388%2898%2900504-0) | Table 3, p. 4, row 10; `ORC-MDJMCVRYSE.1f557a` |  |
| -46 kJ/mol-atom | NbSi2 | 298.15 | experimental |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Chart 1973_ | Table 7, p. 8, row 2; `ORC-OWMXI4C2MG.e1e30a` |  |
| -90.7 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Kaufman 1979_ [doi](https://doi.org/10.1016/0364-5916%2879%2990020-8) | Table 7, p. 8, row 3; `ORC-M6YI3ZG6ZU.664291` |  |
| -59.37 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [5] Liang 1999; _cites Kaufman 1979_ [doi](https://doi.org/10.1016/0364-5916%2879%2990020-8) | Table 2, p. 4, row 7; `ORC-3LN3PBDH7S` |  |
| -59.37 kJ/mol-atom | NbSi2 | 298.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Kaufman 1979_ [doi](https://doi.org/10.1016/0364-5916%2879%2990020-8) | Table 3, p. 6, row 19; `ORC-OONHAKUF7E` |  |
| -56 kJ/mol-atom | NbSi2 | 298.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Fernandes 2002_ [doi](https://doi.org/10.1016/s0966-9795%2802%2900125-5) | Table 3, p. 6, row 20; `ORC-7BGJPC6UD2` |  |
| -56 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [1] Fernandes 2002 | Table 3, p. 6, row 7; `ORC-OBSCZ5RGJF` |  |
| -56 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Fernandes 2002_ [doi](https://doi.org/10.1016/s0966-9795%2802%2900125-5) | Table 7, p. 8, row 8; `ORC-OR7P6CYI7R.950143` |  |
| -56 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Shao 2004_ [doi](https://doi.org/10.1016/j.intermet.2004.03.011) | Table 7, p. 8, row 10; `ORC-T5APMLGDOY.762f19` |  |
| -56 kJ/mol-atom | NbSi2 | 298.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004 | Table 3, p. 6, row 21; `ORC-VHPXKX5UDO` |  |
| -55.5 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Fernandes 2002_ [doi](https://doi.org/10.1016/s0966-9795%2802%2900125-5) | Table 7, p. 8, row 7; `ORC-6A2WC4LPZP.1799de` |  |
| -55.5 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Yang 2003_ [doi](https://doi.org/10.1016/s0966-9795%2803%2900021-9) | Table 7, p. 8, row 9; `ORC-TSPGIBJDSC.6da2bb` |  |
| -55.483 per mol-atom | NbSi2 | 298.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Fernandes 2002_ [doi](https://doi.org/10.1016/s0966-9795%2802%2900125-5) | Table 3, p. 6, row 24; `ORC-5L2QGISI2N` |  |
| -55.467 kJ/mol-atom | NbSi2 | 298.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Yang 2003_ [doi](https://doi.org/10.1016/s0966-9795%2803%2900021-9) | Table 3, p. 6, row 17; `ORC-JRQ5HR4OLC` |  |
| -55.4667 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [1] Fernandes 2002 | Table 3, p. 6, row 6; `ORC-KCTLOGHEMW` |  |
| -53.7 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Meschel 1998_ [doi](https://doi.org/10.1016/s0925-8388%2898%2900504-0) | Table 7, p. 8, row 5; `ORC-AO642VMZO5.7b85c3` |  |
| -51.2033 kJ/mol-atom | (NbSi2) | 273.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [3] Geng 2009 | Table 3, p. 4, row 7; `ORC-M5MZBNJBK5` |  |
| -51.2 kJ/mol (basis unstated) | NbSi2 | 298.15 | model | Calphad | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [6] Utton 2017 | Table 2, p. 6, row 20; `ORC-UEWLRKY6AH` |  |
| -47 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [5] Liang 1999 | Table 2, p. 4, row 5; `ORC-5NMVMEQTMX` |  |
| -47 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Liang 1999_ [doi](https://doi.org/10.1016/s0966-9795%2898%2900073-9) | Table 7, p. 8, row 6; `ORC-LLYIQM4PHA.1e077b` |  |
| -47 kJ/mol-atom | NbSi2 | 298.15 | model | CALPHAD | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Liang 1999_ [doi](https://doi.org/10.1016/s0966-9795%2898%2900073-9) | Table 3, p. 6, row 18; `ORC-QPELC4H3AG` |  |
| -46 kJ/mol-atom | NbSi2 | 298.15 | model | Assessment | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Chart 1973_ | Table 3, p. 6, row 14; `ORC-2ZTCYVL23H` |  |
| -46 kJ/mol-atom | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [5] Liang 1999; _cites Niessen 1981_ [doi](https://doi.org/10.1016/0022-5088%2881%2990200-9) | Table 2, p. 4, row 8; `ORC-5VHEDUXEW4` |  |
| -46 kJ/mol-atom | NbSi2 | 298.15 | model | Assessment | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [2] Shao 2004; _cites Barin 2004_ | Table 3, p. 6, row 16; `ORC-6M6IYNTWXJ` |  |
| -46 kJ/mol-atom | (NbSi2) | 273.15 | model | Assessment | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [3] Geng 2009; _cites Barin 1977_ | Table 3, p. 4, row 8; `ORC-AMMWQUBKMU` |  |
| -46 kJ/mol-atom ± 16 | NbSi2 | 298.15 | model |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [5] Liang 1999; _cites Chart 1973_ | Table 2, p. 4, row 6; `ORC-HGFSOJSSNW` |  |
| -46 kJ/mol-atom | (NbSi2) | 273.15 | model | Assessment | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [3] Geng 2009; _cites Chart 1973_ | Table 3, p. 4, row 9; `ORC-PXRD4KUPTR` |  |
| -49.9 kJ/mol (basis unstated) | NbSi2 | 0 | DFT | ab initio | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [6] Utton 2017; _cites Papadimitriou 2015_ [doi](https://doi.org/10.1007/s11661-015-3149-0) | Table 2, p. 6, row 19; `ORC-AJZQKV43NY` |  |
| -51.5 kJ/mol-atom | NbSi2 | 298.15 | unspecified |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006 | Table 7, p. 8, row 11; `ORC-5B3XLKKPF3.afe0f1` |  |
| -46 kJ/mol-atom | NbSi2 | 298.15 | unspecified |  | [Nb–Si](https://data.orchid-project.org/systems/NB-SI.html) | [4] David 2006; _cites Niessen 1981_ [doi](https://doi.org/10.1016/0022-5088%2881%2990200-9) | Table 7, p. 8, row 4; `ORC-6H3EOWZ5VR.378965` |  |

### 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 NbSi2

| Value | Unit | Printed | Reading | Method (class, basis) | Composition | Scatter | Conversion | Effective |
|---:|---|---:|---:|---|---:|---:|---:|---:|
| -53.7 | kJ/mol-atom |  | 1.667e-4 | 3.5 (unknown, calibrated) |  |  |  | 3.5 |
| -53.7 | kJ/mol-atom | 1.6 | 0.05 | 3.2 (solution_reaction_calorimetry, calibrated) |  |  |  | 3.2 |
| -53.7 | kJ/mol-atom | 1.6 | 1.667e-4 | 3.2 (solution_reaction_calorimetry, calibrated) |  |  |  | 3.2 |
| -46 | kJ/mol-atom |  | 0.5 | 3.5 (unknown, calibrated) |  |  |  | 3.5 |
| -90.7 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -59.37 | kJ/mol-atom |  | 5.000e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -59.37 | kJ/mol-atom |  | 0.005 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -56 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -56 | kJ/mol-atom |  | 1.667e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -56 | kJ/mol-atom |  | 0.5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -56 | kJ/mol-atom |  | 0.5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -56 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -55.5 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -55.5 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -55.483 | per mol-atom |  | 5.000e-4 | unit 'per mol-atom' not convertible to kJ/mol-atom |  |  |  | unit 'per mol-atom' not convertible to kJ/mol-atom |
| -55.467 | kJ/mol-atom |  | 5.000e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -55.4667 | kJ/mol-atom |  | 1.667e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -53.7 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -51.2033 | kJ/mol-atom |  | 1.667e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -51.2 | kJ/mol (basis unstated) |  | 0.05 | 11.7 (model_calculated, calibrated) |  |  |  | 11.7 |
| -47 | kJ/mol-atom |  | 5.000e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -47 | kJ/mol-atom |  | 0.5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -47 | kJ/mol-atom |  | 0.05 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -46 | kJ/mol-atom |  | 0.5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -46 | kJ/mol-atom |  | 5.000e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -46 | kJ/mol-atom |  | 0.5 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -46 | kJ/mol-atom |  | 1.667e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -46 | kJ/mol-atom | 16 | 5.000e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 16 |
| -46 | kJ/mol-atom |  | 1.667e-4 | 3.9 (model_calculated, calibrated) |  |  |  | 3.9 |
| -49.9 | kJ/mol (basis unstated) |  | 0.05 | 29.9 (dft, calibrated) |  |  |  | 29.9 |
| -51.5 | kJ/mol-atom |  | 0.05 | 3.5 (unknown, calibrated) |  |  |  | 3.5 |
| -46 | kJ/mol-atom |  | 0.5 | 3.5 (unknown, calibrated) |  |  |  | 3.5 |

## 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 NbSi2

| Source | Entry | kJ/mol-atom | eV/atom | Space group | E above hull (kJ/mol-atom) | E above hull (eV/atom) | Theoretical |
|---|---|---:|---:|---|---:|---:|---|
| Materials Project | mp-aaaaadri | -48.426 | -0.501906 | P6_222 | 3.000e-4 | 0 | no |
| Materials Project | mp-aaaaarxo | -48.427 | -0.501909 | P6_422 | 0 | 0 | yes |
| OQMD | oqmd-2027994 | -53.117 | -0.550526 | P6222 | 0.0034 | 0 | yes |
| OQMD | oqmd-30789 | -53.121 | -0.550561 | P6422 | 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. P.B. Fernandes, G.C. Coelho, F. Ferreira, C.A. Nunes, B. Sundman, Thermodynamic modeling of the Nb–Si system, Intermetallics 10, 993-999 (2002). [doi:10.1016/s0966-9795(02)00125-5](https://doi.org/10.1016/s0966-9795%2802%2900125-5)
2. G. Shao, Thermodynamic assessment of the Nb–Si–Al system, Intermetallics 12, 655-664 (2004). [doi:10.1016/j.intermet.2004.03.011](https://doi.org/10.1016/j.intermet.2004.03.011)
3. Tai Geng, Changrong Li, Jing Bao, Xinqing Zhao, Zhenmin Du, Cuiping Guo, Thermodynamic assessment of the Nb–Si–Ti system, Intermetallics 17, 343-357 (2009). [doi:10.1016/j.intermet.2008.11.011](https://doi.org/10.1016/j.intermet.2008.11.011)
4. N. David, Y. Cartigny, T. Belmonte, J.M. Fiorani, M. Vilasi, Thermodynamic description of the Cr–Nb–Si isothermal section at 1473K, Intermetallics 14, 464-473 (2006). [doi:10.1016/j.intermet.2005.08.013](https://doi.org/10.1016/j.intermet.2005.08.013)
5. H. Liang, Y.A. Chang, Thermodynamic modeling of the Nb–Si–Ti ternary system, Intermetallics 7, 561-570 (1999). [doi:10.1016/s0966-9795(98)00073-9](https://doi.org/10.1016/s0966-9795%2898%2900073-9)
6. Claire A. Utton, Ioannis Papadimitriou, Hajime Kinoshita, Panos Tsakiropoulos, Experimental and thermodynamic assessment of the Ge-Nb-Si ternary phase diagram, Journal of Alloys and Compounds 717, 303-316 (2017). [doi:10.1016/j.jallcom.2017.04.279](https://doi.org/10.1016/j.jallcom.2017.04.279)

## 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/).