NbSn2: enthalpy of formation

10 accepted literature formation-enthalpy value(s) (experimental 2, model 8); Materials Project -13.422 kJ/mol-atom (mp-aaaaabog); OQMD -19.065 kJ/mol-atom (oqmd-17753).

Systems: Nb–Sn

Literature values

Enthalpy of formation of NbSn2 reported in the literature (10)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-18.21 kJ/mol (basis unstated) ± 0.81	NbSn2	860	experimental	Electromotive force	Nb–Sn	[1] Toffolon 1998 cites ref. 75Mal	Table 3, p. 2, row 1 report
-18.21 kJ/mol (basis unstated) ± 0.81	NbSn2	860	experimental	Electromotive force	Nb–Sn	[2] Toffolon 2002 cites Malets 1975	Table 4, p. 3, row 1 report
-20.143 kJ/mol-atom	NbSn2	860	model		Nb–Sn	[2] Toffolon 2002	Table 4, p. 3, row 6 report
-17.585 kJ/mol (basis unstated)	NbSn2	298.15	model	Optimization	Nb–Sn	[1] Toffolon 1998	Table 3, p. 2, row 4 report
-17.585 kJ/mol-atom	NbSn2	860	model		Nb–Sn	[2] Toffolon 2002 cites Toffolon 2002	Table 4, p. 3, row 3 report
-17.585 kJ/mol (basis unstated)	NbSn2	860	model	Optimization	Nb–Sn	[1] Toffolon 1998	Table 3, p. 2, row 3 report
-17.585 kJ/mol-atom	NbSn2	298.15	model		Nb–Sn	[2] Toffolon 2002 cites Toffolon 2002	Table 4, p. 3, row 4 report
-16 kJ/mol-atom	NbSn2	298.15	model		Nb–Sn	[2] Toffolon 2002 cites ref. 1988Deb	Table 4, p. 3, row 2 report
-16 kJ/mol (basis unstated)	NbSn2	298.15	model	Calculation	Nb–Sn	[1] Toffolon 1998 cites ref. 88Deb	Table 3, p. 2, row 2 report
-15.495 kJ/mol-atom	NbSn2	298.15	model		Nb–Sn	[2] Toffolon 2002	Table 4, p. 3, row 5 report

Uncertainty budget

Components kept separate, in the value's unit (literature SCHEMA.md, 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.

Uncertainty budget of the literature values of NbSn2
Value	Unit	Printed	Reading	Method (class, basis)	Effective
-18.21	kJ/mol (basis unstated)	0.81	5.000e-4	13.8 (emf, cleaned_below_threshold)	13.8
-18.21	kJ/mol (basis unstated)	0.81	0.005	13.8 (emf, cleaned_below_threshold)	13.8
-20.143	kJ/mol-atom		5.000e-4	3.9 (model_calculated, calibrated)	3.9
-17.585	kJ/mol (basis unstated)		5.000e-4	11.7 (model_calculated, calibrated)	11.7
-17.585	kJ/mol-atom		5.000e-4	3.9 (model_calculated, calibrated)	3.9
-17.585	kJ/mol (basis unstated)		5.000e-4	11.7 (model_calculated, calibrated)	11.7
-17.585	kJ/mol-atom		5.000e-4	3.9 (model_calculated, calibrated)	3.9
-16	kJ/mol-atom		0.05	3.9 (model_calculated, calibrated)	3.9
-16	kJ/mol (basis unstated)		5.000e-4	11.7 (model_calculated, calibrated)	11.7
-15.495	kJ/mol-atom		5.000e-4	3.9 (model_calculated, calibrated)	3.9

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.

DFT formation energy of NbSn2
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaaaabog	-13.422	-0.139109	Fddd	0	0	no
OQMD	oqmd-17753	-19.065	-0.197594	Fddd	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 (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 (CC BY 4.0);

Sources

C. Toffolon, C. Servant, B. Sundman, Thermodynamic assessment of the Nb-Sn system, JPE 19, 479-485 (1998). doi:10.1361/105497198770341978
C. Toffolon, C. Servant, J. C. Gachon, B. Sundman, Reassessment of the Nb-Sn system, JPE 23, 134-139 (2002). doi:10.1361/1054971023604071

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). doi: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). doi: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). doi: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.

@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}
}