NbSi2: enthalpy of formation

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

Literature values

Enthalpy of formation of NbSi2 reported in the literature (32)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-53.7 kJ/mol-atom	NbSi2	298.15	experimental		Nb–Si	[1] Fernandes 2002 cites Meschel 1998 doi	Table 3, p. 6, row 8 report
-53.7 kJ/mol-atom ± 1.6	NbSi2	298.15	experimental	Calorimetry	Nb–Si	[2] Shao 2004 cites Meschel 1998 doi	Table 3, p. 6, row 15 report
-53.7 kJ/mol-atom ± 1.6	(NbSi2)	273.15	experimental	Calorimetry	Nb–Si	[3] Geng 2009 cites Meschel 1998 doi	Table 3, p. 4, row 10 report
-46 kJ/mol-atom	NbSi2	298.15	experimental		Nb–Si	[4] David 2006 cites Chart 1973	Table 7, p. 8, row 2 report
-90.7 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Kaufman 1979 doi	Table 7, p. 8, row 3 report
-59.37 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[5] Liang 1999 cites Kaufman 1979 doi	Table 2, p. 4, row 7 report
-59.37 kJ/mol-atom	NbSi2	298.15	model	CALPHAD	Nb–Si	[2] Shao 2004 cites Kaufman 1979 doi	Table 3, p. 6, row 19 report
-56 kJ/mol-atom	NbSi2	298.15	model	CALPHAD	Nb–Si	[2] Shao 2004 cites Fernandes 2002 doi	Table 3, p. 6, row 20 report
-56 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[1] Fernandes 2002	Table 3, p. 6, row 7 report
-56 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Fernandes 2002 doi	Table 7, p. 8, row 8 report
-56 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Shao 2004 doi	Table 7, p. 8, row 10 report
-56 kJ/mol-atom	NbSi2	298.15	model	CALPHAD	Nb–Si	[2] Shao 2004	Table 3, p. 6, row 21 report
-55.5 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Fernandes 2002 doi	Table 7, p. 8, row 7 report
-55.5 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Yang 2003 doi	Table 7, p. 8, row 9 report
-55.483 per mol-atom	NbSi2	298.15	model	CALPHAD	Nb–Si	[2] Shao 2004 cites Fernandes 2002 doi	Table 3, p. 6, row 24 report
-55.467 kJ/mol-atom	NbSi2	298.15	model	CALPHAD	Nb–Si	[2] Shao 2004 cites Yang 2003 doi	Table 3, p. 6, row 17 report
-55.4667 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[1] Fernandes 2002	Table 3, p. 6, row 6 report
-53.7 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Meschel 1998 doi	Table 7, p. 8, row 5 report
-51.2033 kJ/mol-atom	(NbSi2)	273.15	model	CALPHAD	Nb–Si	[3] Geng 2009	Table 3, p. 4, row 7 report
-51.2 kJ/mol (basis unstated)	NbSi2	298.15	model	Calphad	Nb–Si	[6] Utton 2017	Table 2, p. 6, row 20 report
-47 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[5] Liang 1999	Table 2, p. 4, row 5 report
-47 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[4] David 2006 cites Liang 1999 doi	Table 7, p. 8, row 6 report
-47 kJ/mol-atom	NbSi2	298.15	model	CALPHAD	Nb–Si	[2] Shao 2004 cites Liang 1999 doi	Table 3, p. 6, row 18 report
-46 kJ/mol-atom	NbSi2	298.15	model	Assessment	Nb–Si	[2] Shao 2004 cites Chart 1973	Table 3, p. 6, row 14 report
-46 kJ/mol-atom	NbSi2	298.15	model		Nb–Si	[5] Liang 1999 cites Niessen 1981 doi	Table 2, p. 4, row 8 report
-46 kJ/mol-atom	NbSi2	298.15	model	Assessment	Nb–Si	[2] Shao 2004 cites Barin 2004	Table 3, p. 6, row 16 report
-46 kJ/mol-atom	(NbSi2)	273.15	model	Assessment	Nb–Si	[3] Geng 2009 cites Barin 1977	Table 3, p. 4, row 8 report
-46 kJ/mol-atom ± 16	NbSi2	298.15	model		Nb–Si	[5] Liang 1999 cites Chart 1973	Table 2, p. 4, row 6 report
-46 kJ/mol-atom	(NbSi2)	273.15	model	Assessment	Nb–Si	[3] Geng 2009 cites Chart 1973	Table 3, p. 4, row 9 report
-49.9 kJ/mol (basis unstated)	NbSi2	0	DFT	ab initio	Nb–Si	[6] Utton 2017 cites Papadimitriou 2015 doi	Table 2, p. 6, row 19 report
-51.5 kJ/mol-atom	NbSi2	298.15	unspecified		Nb–Si	[4] David 2006	Table 7, p. 8, row 11 report
-46 kJ/mol-atom	NbSi2	298.15	unspecified		Nb–Si	[4] David 2006 cites Niessen 1981 doi	Table 7, p. 8, row 4 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 NbSi2
Value	Unit	Printed	Reading	Method (class, basis)	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.

DFT formation energy of NbSi2
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	Theoretical
Materials Project	mp-aaaaadri	-48.426	-0.501906	P6_222	3.000e-4	no
Materials Project	mp-aaaaarxo	-48.427	-0.501909	P6_422	0	yes
OQMD	oqmd-2027994	-53.117	-0.550526	P6222	0.0034	yes
OQMD	oqmd-30789	-53.121	-0.550561	P6422	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

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
G. Shao, Thermodynamic assessment of the Nb–Si–Al system, Intermetallics 12, 655-664 (2004). doi:10.1016/j.intermet.2004.03.011
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
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
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
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

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}
}