MgB7: enthalpy of formation

7 accepted literature formation-enthalpy value(s) (experimental 5, model 2); experimental median -14.45 kJ/mol-atom (n = 4); Materials Project -12.598 kJ/mol-atom (mp-aaacdrdz); OQMD -13.076 kJ/mol-atom (oqmd-23820).

Systems: B–Mg

Literature values

Enthalpy of formation of MgB7 reported in the literature (7)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-20.3 per mol-atom ± 1.5	MgB7	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 13 report
-20.3 kJ/mol-atom ± 1.5	MgB7	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 13 report
-15.5 kJ/mol-atom ± 2.1	MgB7	298.15	experimental	Vap. p.	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 15 report
-13.4 kJ/mol-atom	MgB7	298.15	experimental	calorimetry	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 17 report
-13.4 kJ/mol-atom ± 0.6	MgB7	298.15	experimental	calorimetry	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 16 report
-18.9 per mol-atom	MgB7	298.15	model	Ph. diagr. assessment	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 14 report
-18.9 kJ/mol-atom	MgB7	298.15	model	Ph. diagr. assessment	B–Mg	[1] Balducci 2005	Table 2, p. 4, row 14 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 MgB7
Value	Unit	Printed	Reading	Method (class, basis)	Effective
-20.3	per mol-atom	1.5	0.05	unit 'per mol-atom' not convertible to kJ/mol-atom	1.5
-20.3	kJ/mol-atom	1.5	0.05	4.2 (kems_vapour, calibrated)	4.2
-15.5	kJ/mol-atom	2.1	0.05	4.2 (kems_vapour, calibrated)	4.2
-13.4	kJ/mol-atom		0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-13.4	kJ/mol-atom	0.6	0.05	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-18.9	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
-18.9	kJ/mol-atom		0.05	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 MgB7
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaacdrdz	-12.598	-0.130571	Imma	0	0	no
OQMD	oqmd-23820	-13.076	-0.135526	Imma	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

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}
}