MgB2: enthalpy of formation

15 accepted literature formation-enthalpy value(s) (experimental 11, model 4); experimental median -18.6 kJ/mol-atom (n = 7); Materials Project -12.577 kJ/mol-atom (mp-aaaaabdj); OQMD -13.509 kJ/mol-atom (oqmd-98302).

Systems: B–Mg

Literature values

Enthalpy of formation of MgB2 reported in the literature (15)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-41.1 per mol-atom ± 2.2	MgB2	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 1 report
-41.1 kJ/mol-atom ± 2.2	MgB2	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 1 report
-26.66 kJ/mol-atom ± 10	MgB2	298.15	experimental	vapor pressure	B–Mg	[2] Liu 2001 cites Jansson 1984	Table 2, p. 2, row 1 report
-26.6 per mol-atom ± 10	MgB2	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 4 report
-26.6 kJ/mol-atom ± 10	MgB2	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 4 report
-18.6 kJ/mol-atom	MgB2	298.15	experimental	calorimetry	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 6 report
-18.6 per mol-atom	MgB2	298.15	experimental	calorimetry	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 6 report
-18.55 kJ/mol-atom ± 1.12	MgB2	298.15	experimental	calorimetry	B–Mg	[2] Liu 2001 cites Sundman 1985 doi	Table 2, p. 2, row 7 report
-17.2 kJ/mol-atom ± 1.4	MgB2	298.15	experimental	calorimetry	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 5 report
-17.2 per mol-atom ± 1.4	MgB2	298.15	experimental	calorimetry	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 5 report
-17.17 kJ/mol-atom ± 1.39	MgB2	298.15	experimental	calorimetry	B–Mg	[2] Liu 2001 cites Jansson 1984	Table 2, p. 2, row 4 report
-35.9 kJ/mol-atom	MgB2	298.15	model	Ph. diagr. assessment	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 2 report
-35.9 per mol-atom	MgB2	298.15	model	Ph. diagr. assessment	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 2 report
-24 kJ/mol-atom	MgB2	298.15	model	Ph. diagr. assessment	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 3 report
-24 per mol-atom	MgB2	298.15	model	Ph. diagr. assessment	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 3 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 MgB2
Value	Unit	Printed	Reading	Method (class, basis)	Effective
-41.1	per mol-atom	2.2	0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	2.2
-41.1	kJ/mol-atom	2.2	0.05	4.2 (kems_vapour, calibrated)	4.2
-26.66	kJ/mol-atom	10	0.005	4.2 (kems_vapour, calibrated)	10
-26.6	per mol-atom	10	0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	10
-26.6	kJ/mol-atom	10	0.05	4.2 (kems_vapour, calibrated)	10
-18.6	kJ/mol-atom		0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-18.6	per mol-atom		0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	unit 'per mol-atom' not convertible to kJ/mol-atom
-18.55	kJ/mol-atom	1.12	0.005	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-17.2	kJ/mol-atom	1.4	0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-17.2	per mol-atom	1.4	0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	1.4
-17.17	kJ/mol-atom	1.39	0.005	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-35.9	kJ/mol-atom		0.05	3.9 (model_calculated, calibrated)	3.9
-35.9	per mol-atom		0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	unit 'per mol-atom' not convertible to kJ/mol-atom
-24	kJ/mol-atom		0.05	3.9 (model_calculated, calibrated)	3.9
-24	per mol-atom		0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	unit 'per mol-atom' not convertible to kJ/mol-atom

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 MgB2
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaaaabdj	-12.577	-0.130355	P6/mmm	0	0	no
OQMD	oqmd-98302	-13.509	-0.140012	P6/mmm	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

G. Balducci, S. Brutti, A. Ciccioli, G. Gigli, P. Manfrinetti, A. Palenzona et al., Thermodynamics of the intermediate phases in the Mg–B system, Journal of Physics and Chemistry of Solids 66, 292-297 (2005). doi:10.1016/j.jpcs.2004.06.063
Zi-Kui Liu, Yu Zhong, D.G. Schlom, X.X. Xi, Qi Li, Computational thermodynamic modeling of the Mg-B system, Calphad 25, 299-303 (2001). doi:10.1016/s0364-5916(01)00050-5

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}
}