Fe–Hf system

32 accepted literature values from 1 paper(s) (experimental 13, model 19); 1 calculated phase diagram(s). 2 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: JSON · CSV · interactive explorer · interactive phase diagram · phases (8) · papers (bibliography) · Markdown

Accepted values by evidence class
Evidence class	Values
experimental	13
model	19

Accepted values by property group
Property group	Values
invariant reaction	14
phase transition	5
formation	12
heat capacity / entropy / enthalpy	1

Calculated phase diagrams

Binary phase diagrams calculated with pycalphad 0.11.2 from the SGTE binary collection (Hallstedt 2025, CC BY 4.0). Evidence class: model.

Assessments with a calculated phase diagram
TDB file	Assessment	SHA-256	Links
FeHf-08Idb.tdb	M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, J. Alloys Compd., 456, 151-58(2008). doi:10.1016/j.jallcom.2007.02.036	`2a85ddea9bbae84b610150905ff4dcd238fbf61cba0fab193be31db3d1d84dbd`	viewer · TDB · JSON

Calculated three-phase invariants (model, mole fraction of the second component)
TDB file	T (K)	Phases at the invariant
FeHf-08Idb.tdb	1933.37	FE2HF_C14 (x(Hf) 0.31962) + FE2HF_C36 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.4884)
FeHf-08Idb.tdb	1933.37	FE2HF_C14 (x(Hf) 0.31961) + FE2HF_C36 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.48833)
FeHf-08Idb.tdb	1661.09	BCC_A2 (x(Hf) 0.0029) + LIQUID (x(Hf) 0.06067) + FE2HF_C14 (x(Hf) 0.24546)
FeHf-08Idb.tdb	1607.59	FCC_A1 (x(Hf) 1.800e-4) + BCC_A2 (x(Hf) 0.00221) + FE2HF_C14 (x(Hf) 0.24504)
FeHf-08Idb.tdb	1607.59	FCC_A1 (x(Hf) 1.800e-4) + BCC_A2 (x(Hf) 0.00221) + FE2HF_C14 (x(Hf) 0.24504)
FeHf-08Idb.tdb	1573.55	FE2HF_C36 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.64718) + BCC_A2 (x(Hf) 0.87781)
FeHf-08Idb.tdb	1573.55	FE2HF_C36 (x(Hf) 0.33333) + LIQUID (x(Hf) 0.6472) + BCC_A2 (x(Hf) 0.87783)
FeHf-08Idb.tdb	1531.26	FE2HF_C36 (x(Hf) 0.33333) + FEHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.87902)
FeHf-08Idb.tdb	1531.26	FE2HF_C36 (x(Hf) 0.33333) + FEHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.879)
FeHf-08Idb.tdb	1531.26	FE2HF_C36 (x(Hf) 0.33333) + FEHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.87901)
FeHf-08Idb.tdb	1508.56	FEHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.88276) + HCP_A3 (x(Hf) 1)
FeHf-08Idb.tdb	1508.56	FEHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.88282) + HCP_A3 (x(Hf) 1)
FeHf-08Idb.tdb	1508.56	FEHF2 (x(Hf) 0.66667) + BCC_A2 (x(Hf) 0.88283) + HCP_A3 (x(Hf) 1)
FeHf-08Idb.tdb	1474.54	FE2HF_C36 (x(Hf) 0.33333) + FE2HF_C15 (x(Hf) 0.33333) + FEHF2 (x(Hf) 0.66667)
FeHf-08Idb.tdb	1474.54	FE2HF_C14 (x(Hf) 0.31727) + FE2HF_C15 (x(Hf) 0.33333) + FE2HF_C36 (x(Hf) 0.33333)
FeHf-08Idb.tdb	1474.54	FE2HF_C14 (x(Hf) 0.31727) + FE2HF_C36 (x(Hf) 0.33333) + FE2HF_C15 (x(Hf) 0.33333)
FeHf-08Idb.tdb	1185.91	FCC_A1 (x(Hf) 1.000e-5) + BCC_A2 (x(Hf) 1.100e-4) + FE2HF_C14 (x(Hf) 0.243)
FeHf-08Idb.tdb	1185.91	FCC_A1 (x(Hf) 1.000e-5) + BCC_A2 (x(Hf) 1.100e-4) + FE2HF_C14 (x(Hf) 0.243)

Convex hulls: Materials Project DFT hull · OQMD DFT hull

Invariant reactions (literature)

Invariant reactions reported in the literature for the Fe–Hf system (14)
T (K)	Reaction / phases	Compositions (mole fraction)	Class	Source	Location
1914.15	Liq + λ -> βFe2Hf	Liq: Hf 0.5016; λ: Hf 0.3209	model	[1] Idbenali 2008	Table 4, p. 5, row 14 report
1913.15	Liq + λ -> βFe2Hf	Liq: Hf 0.482; λ: Hf 0.0327	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 13 report
1663.15	eutectic: Liq -> (δFe) + λ	Liq: Hf 0.079; (δFe): Hf 0.0145; λ: Hf 0.251	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 11 report
1662.15	eutectic: Liq -> (δFe) + λ	Liq: Hf 0.0604; (δFe): Hf 0.00288; λ: Hf 0.2454	model	[1] Idbenali 2008	Table 4, p. 5, row 12 report
1608.15	(γFe) -> (δFe) + λ	(γFe): Hf 0.0022; (δFe): Hf 1.800e-4; λ: Hf 0.245	model	[1] Idbenali 2008	Table 4, p. 5, row 10 report
1603.15	(γFe) -> (δFe) + λ	(γFe): Hf 0.00835; (δFe): Hf 0.0051; λ: Hf 0.257	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 9 report
1574.15	eutectic: Liq -> (βHf) + βFe2Hf	Liq: Hf 0.6472; (βHf): Hf 0.8788	model	[1] Idbenali 2008	Table 4, p. 5, row 8 report
1573.15	eutectic: Liq -> (βHf) + βFe2Hf	Liq: Hf 0.639; (βHf): Hf 0.955	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 7 report
1533.15	(βHf) + βFe2Hf -> FeHF2	(βHf): Hf 0.964	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 5 report
1533.15	(βHf) + βFe2Hf -> FeHF2	(βHf): Hf 0.879	model	[1] Idbenali 2008	Table 4, p. 5, row 6 report
1509.15	(βHf) -> (αHf) + FeHF2	(βHf): Hf 0.8828; (αHf): Hf 1	model	[1] Idbenali 2008	Table 4, p. 5, row 4 report
1508.15	(βHf) -> (αHf) + FeHF2	(βHf): Hf 0.97; (αHf): Hf 0.99	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 3 report
1186.15	(αFe) -> (γFe) + λ	(αFe): Hf 1.060e-4; (γFe): Hf 1.300e-5; λ: Hf 0.243	model	[1] Idbenali 2008	Table 4, p. 5, row 18 report
1185.15	(αFe) -> (γFe) + λ	(αFe): Hf 0.00196; λ: Hf 0.281	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 17 report

Formation enthalpies

Literature values in kJ/mol-atom where the per-atom basis is known. DFT columns: the lowest-energy entry at the same composition (Materials Project 2026.04.13, OQMD v1.8; different energy references, never averaged), from dft_parity.json.

Enthalpies of formation, Fe–Hf system (12)
Phase	Compound	Value	T (K)	Class	MP DFT (kJ/mol-atom)	OQMD DFT (kJ/mol-atom)	Source	Location
Fe2Hf-HT	Fe2Hf	-40.33 kJ/mol-atom	1723	model	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008	Table 2, p. 3, row 5 report
Fe2Hf-HT	Fe2Hf	-39.4 kJ/mol-atom ± 4.3	1723	experimental	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008 cites Gachon 1992 doi	Table 2, p. 3, row 1 report
Fe2Hf-HT	Fe2Hf	-28 kJ/mol-atom	298.15	model	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008 cites Niessen 1983 doi	Table 2, p. 3, row 3 report
Fe2Hf-HT	Fe2Hf	-25 kJ/mol-atom		model	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008 cites Colinet 1985 doi	Table 2, p. 3, row 2 report
Fe2Hf-HT	Fe2Hf	-12.3 kJ/mol-atom ± 1.1	1373	experimental	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008 cites Meschel 2006 doi	Table 2, p. 3, row 4 report
Fe2Hf-LT	Fe2Hf	-39.86 kJ/mol-atom	1460	model	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008	Table 2, p. 3, row 7 report
Fe2Hf-LT	Fe2Hf	-39.847 kJ/mol-atom	1480	model	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008	Table 2, p. 3, row 6 report
Fe2Hf-LT	Fe2Hf	-34.525 kJ/mol-atom	298.15	model	-33.396 (mp-aaaaaamv)	-33.317 (oqmd-30206)	[1] Idbenali 2008	Table 2, p. 3, row 8 report
FeHf2	FeHf2	-24 kJ/mol-atom ± 3.5	1493	experimental	-17.607 (mp-aaaaaeby)	-17.862 (oqmd-18331)	[1] Idbenali 2008 cites Gachon 1992 doi	Table 2, p. 3, row 9 report
FeHf2	FeHf2	-23.9 kJ/mol-atom	1493	model	-17.607 (mp-aaaaaeby)	-17.862 (oqmd-18331)	[1] Idbenali 2008	Table 2, p. 3, row 12 report
FeHf2	FeHf2	-23 kJ/mol-atom	298.15	model	-17.607 (mp-aaaaaeby)	-17.862 (oqmd-18331)	[1] Idbenali 2008 cites Niessen 1983 doi	Table 2, p. 3, row 11 report
FeHf2	FeHf2	-22 kJ/mol-atom		model	-17.607 (mp-aaaaaeby)	-17.862 (oqmd-18331)	[1] Idbenali 2008 cites Yu 1973	Table 2, p. 3, row 10 report

Other properties

Phase transition (5)

Phase transition, Fe–Hf system
Property	Value	T (K)	Phases / composition	Class	Source	Location	Quote
Phase transition	1473 K	1473	Fe2Hf LT + Fe2Hf HT	model	[1] Idbenali 2008 cites Okamoto 2000	p. 1 report	According to the evaluation by Okamoto [4], the stoichiometric Fe2 Hf phase presents a crystalline transition at 1473 K from C15 (noted as ␣Fe2 Hf or Fe2 Hf cub or Fe2 Hf LT (low temperature), Cu2 Mg type) to C36 type (␤Fe2 Hf or Fe2 Hf hex2 or Fe2 Hf HT (high temperature), Ni2 Mg type).
Phase transition	1473.15 K	1473.15	Fe2Hf-LT -> Fe2Hf-HT Fe2Hf-LT: Hf 0.3333	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 1 report
Phase transition	1473.15 K	1473.15	Fe2Hf-LT -> Fe2Hf-HT Fe2Hf-LT: Hf 0.3333	model	[1] Idbenali 2008	Table 4, p. 5, row 2 report
Phase transition	2093.15 K	2093.15	(Liq -> λ Liq: Hf 0.298	experimental	[1] Idbenali 2008 cites Svechnikov 1961	Table 4, p. 5, row 15 report
Phase transition	2094.15 K	2094.15	(Liq -> λ Liq: Hf 0.3	model	[1] Idbenali 2008	Table 4, p. 5, row 16 report

Heat capacity / entropy / enthalpy (1)

Heat capacity / entropy / enthalpy, Fe–Hf system
Property	Value	T (K)	Phases / composition	Class	Source	Location	Quote
Heat capacity printed: cp	56 J mol-1 K-1	650		experimental	[1] Idbenali 2008 cites Ivanovic 1995 doi	p. 1 report	Its specific heat has been determined in the 300-800 K temperature range by [16]. It first increases from 78 to 88 J mol-1 K-1 , then a pronounced drop starts around 470 K up to about 650 K (cp = 56 J mol-1 K-1 ), then the specific heat increases again from 700 K.

Sources

Reporting papers the values were read from (a value cited from another work names that work in its row).

M. Idbenali, N. Selhaoui, L. Bouirden, C. Servant, Thermodynamic assessment of the Fe–Hf binary system, Journal of Alloys and Compounds 456, 151-158 (2008). doi:10.1016/j.jallcom.2007.02.036

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-Diagrams: calculated binary phase diagrams (version 2026.10), Zenodo (2026). doi:10.5281/zenodo.23735859
R. Arróyave, J. Saal, D. Shin, ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD) (version 2026.10), Zenodo (2026). doi:10.5281/zenodo.23735891
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); 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; 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). 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_phase_diagrams_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Diagrams: calculated binary phase diagrams}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735859},
  url       = {https://doi.org/10.5281/zenodo.23735859}
}

@misc{orchid_hulls_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Hulls: binary convex hulls (Materials Project, OQMD, assessed CALPHAD)}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735891},
  url       = {https://doi.org/10.5281/zenodo.23735891}
}

@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}
}