C–Hf system

42 accepted literature values from 2 paper(s) (experimental 23, model 8, unspecified 11); 0 calculated phase diagram(s). 8 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: JSON · CSV · interactive explorer · phases (6) · papers (bibliography) · Markdown

Accepted values by evidence class
Evidence class	Values
experimental	23
model	8
unspecified	11

Accepted values by property group
Property group	Values
invariant reaction	15
formation	13
heat capacity / entropy / enthalpy	7
crystal structure	7

Convex hulls: Materials Project DFT hull · OQMD DFT hull · CALPHAD hull HfC-97Bit-LB

Invariant reactions (literature)

Invariant reactions reported in the literature for the C–Hf system (15)
T (K)	Reaction / phases	Compositions (mole fraction)	Class	Source	Location
4223	congruent melting: L <-> HfC1-x	L: C 0.485; HfC1-x: C 0.485	unspecified	[1] Bittermann 1997 cites ref. 2	Table 1, p. 2, row 17 report
4215	congruent melting: L <-> HfC1-x	L: C 0.484; HfC1-x: C 0.484	model	[1] Bittermann 1997	Table 1, p. 2, row 18 report
4201	congruent melting: L <-> HfC1-x	L: C 0.485; HfC1-x: C 0.485	experimental	[1] Bittermann 1997 cites Rudy 1965	Table 1, p. 2, row 16 report
3453	eutectic: L <-> HfC1-x + C	L: C 0.65; HfC1-x: C 0.495	experimental	[1] Bittermann 1997 cites Rudy 1965	Table 1, p. 2, row 13 report
3453	eutectic: L <-> HfC1-x + C	L: C 0.68; HfC1-x: C 0.495	unspecified	[1] Bittermann 1997 cites Rudy 1969	Table 1, p. 2, row 14 report
3446	eutectic: L <-> HfC1-x + C	L: C 0.68; HfC1-x: C 0.499; C: C 1	model	[1] Bittermann 1997	Table 1, p. 2, row 15 report
2649	peritectic: L + HfC1-x <-> αHf	L: C 0.0602; HfC1-x: C 0.335; αHf: C 0.14	model	[1] Bittermann 1997	Table 1, p. 2, row 12 report
2633	peritectic: L + HfC1-x <-> αHf	L: C 0.05; HfC1-x: C 0.34; αHf: C 0.15	unspecified	[1] Bittermann 1997 cites ref. 2	Table 1, p. 2, row 11 report
2633	peritectic: L + HfC1-x <-> αHf	L: C 0.05; HfC1-x: C 0.34; αHf: C 0.14	experimental	[1] Bittermann 1997 cites Rudy 1965	Table 1, p. 2, row 10 report
2506	congruent melting: L <-> βHf	L: C 0; βHf: C 0	model	[1] Bittermann 1997	Table 1, p. 2, row 9 report
2504	congruent melting: L <-> βHf	L: C 0; βHf: C 0	unspecified	[1] Bittermann 1997 cites ref. 2	Table 1, p. 2, row 8 report
2491	eutectic: L <-> βHf + αHf	L: C 0.015; βHf: C 0.01; αHf: C 0.02	unspecified	[1] Bittermann 1997 cites ref. 2	Table 1, p. 2, row 5 report
2491	congruent melting: L <-> βHf	L: C 0; βHf: C 0	experimental	[1] Bittermann 1997 cites Rudy 1965	Table 1, p. 2, row 7 report
2480	eutectic: L <-> βHf + αHf	L: C 0.0137; βHf: C 0.005; αHf: C 0.0293	model	[1] Bittermann 1997	Table 1, p. 2, row 6 report
2453	eutectic: L <-> βHf + αHf	L: C 0.015; βHf: C 0.01; αHf: C 0.02	experimental	[1] Bittermann 1997 cites Rudy 1965	Table 1, p. 2, row 4 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, C–Hf system (13)
Phase	Value	T (K)	Class	Source	Location	Quote
HfC	-262.7 kJ/mol (basis unstated)	298.15	experimental	[1] Bittermann 1997 cites Coffman 1963	Table 3, p. 3, row 1 report
HfC	-210.5 kJ/mol (basis unstated) ± 20.9	298.15	experimental	[1] Bittermann 1997 cites Fesenko 1966	Table 3, p. 3, row 5 report
HfC	-209.4 kJ/mol (basis unstated)	298.15	model	[1] Bittermann 1997	Table 3, p. 3, row 9 report
HfC	-209.4 kJ/mol (basis unstated)	298.15	experimental	[1] Bittermann 1997 cites ref. 77Kor	p. 7 report	Thus, the value Ae/-/(HfC, 298 K) = -209.4 kJ/mol from [77Kor] was selected in the present assessment, which was also confirmed by the calculation of the phase relations in the ternary Hf-B-C system [97Bit].
HfC0.6	-140.9 kJ/mol (basis unstated)	298.15	experimental	[1] Bittermann 1997 cites ref. 77Kor	Table 3, p. 3, row 6 report
HfC0.621	-133.1 kJ/mol (basis unstated)	1780	experimental	[1] Bittermann 1997 cites ref. 89Ber	Table 3, p. 3, row 8 report
HfC0.67	-220.9 kJ/mol (basis unstated) ± 1.7	298.15	experimental	[1] Bittermann 1997 cites Zehlankin 1964	Table 3, p. 3, row 4 report
HfC0.93	-197.5 kJ/mol (basis unstated) ± 3.8	298.15	experimental	[1] Bittermann 1997 cites Maslov 1978	Table 3, p. 3, row 7 report
HfC0.958	-218.4 kJ/mol (basis unstated) ± 1.7	298.15	experimental	[1] Bittermann 1997 cites Mah 1964	Table 3, p. 3, row 2 report
HfC0.97	-238.1 kJ/mol (basis unstated) ± 29.3	298.15	experimental	[1] Bittermann 1997 cites McClaine 1964	Table 3, p. 3, row 3 report
HfC0.980	-209.7 kJ/mol (basis unstated) ± 13.5	1780	experimental	[1] Bittermann 1997 cites ref. 89Ber	Table 3, p. 3, row 8 report
HfC1.0	-209.4 kJ/mol (basis unstated)	298.15	experimental	[1] Bittermann 1997 cites ref. 77Kor	Table 3, p. 3, row 6 report
HfC1.00	-231.1 kJ/mol (basis unstated) ± 2.1	298.15	experimental	[1] Bittermann 1997 cites Zehlankin 1964	Table 3, p. 3, row 4 report

Other properties

Heat capacity / entropy / enthalpy (7)

Heat capacity / entropy / enthalpy, C–Hf system
Property	Value	T (K)	Phases / composition	Class	Source	Location
Entropy printed: Derived S298	39.64 unknown	298.15	HfC alloy: Hf 0.5	model	[1] Bittermann 1997	Table 4a, p. 5, row 5 report
Entropy printed: Derived S298	39.5 unknown ± 0.42	298.15	HfC0.96 alloy: Hf 0.510204	experimental	[1] Bittermann 1997 cites McClaine 1964	Table 4a, p. 5, row 1 report
Entropy printed: Derived S298	39.36 unknown	298.15	HfC0.968 alloy: Hf 0.50813	experimental	[1] Bittermann 1997 cites E 1977	Table 4a, p. 5, row 4 report
Heat capacity printed: Cp (298)	37.56 J/mol (basis unstated)/K	298.15	HfC alloy: Hf 0.5	model	[1] Bittermann 1997	Table 4a, p. 5, row 5 report
Heat capacity printed: Cp (298)	37.49 J/mol (basis unstated)/K	298.15	HfC0.96 alloy: Hf 0.510204	experimental	[1] Bittermann 1997 cites McClaine 1964	Table 4a, p. 5, row 1 report
Heat capacity printed: Cp (298)	37.37 J/mol (basis unstated)/K	298.15	HfC0.968 alloy: Hf 0.50813	experimental	[1] Bittermann 1997 cites E 1977	Table 4a, p. 5, row 4 report
Heat capacity printed: Cp (298)	41.82 J/mol (basis unstated)/K	298.15	HfC0.99 alloy: Hf 0.502513	experimental	[1] Bittermann 1997 cites Buravoi 1974	Table 4a, p. 5, row 3 report

Crystal structure (7)

Crystal structure, C–Hf system
Property	Value	T (K)	Phases / composition	Class	Source	Location
Lattice a	2.4612 Å	298.15	(C) alloy: Hf 0	unspecified	[1] Bittermann 1997 cites ref. 2	Table 2, p. 2, row 3 report
Lattice a	3.1946 Å	298.15	(αHf) (αHf): C 0.15, Hf 0.85	unspecified	[1] Bittermann 1997	Table 2, p. 2, row 1 report
Lattice a	4.62225 Å (range 4.606 to 4.6385)	298.15	HfC1−x	experimental	[1] Bittermann 1997 cites Rudy 1969	Table 2, p. 2, row 4 report
Lattice a	4.6385 Å	3942 (<)	HfC1-x HfC1-x: C 0.495	unspecified	[2] Bittermann 2002 cites ref. 1969Rud	Table 1, p. 4, row 21 report
Lattice c	6.709 Å	298.15	(C) alloy: Hf 0	unspecified	[1] Bittermann 1997 cites ref. 2	Table 2, p. 2, row 3 report
Lattice c	5.051 Å	298.15	(αHf) (αHf): C 0.15, Hf 0.85	unspecified	[1] Bittermann 1997	Table 2, p. 2, row 1 report
lattice c a	2.7258 not_printed	298.15	(C) alloy: Hf 0	unspecified	[1] Bittermann 1997 cites ref. 2	Table 2, p. 2, row 3 report

Sources

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

H. Bittermann, P. Rogl, Critical assessment and thermodynamic calculation of the binary system hafnium-carbon (Hf-C), JPE 18, 344-356 (1997). doi:10.1007/s11669-997-0061-3
H. Bittermann, P. Rogl, Critical assessment and thermodynamic calculation of the ternary system C-Hf-Zr (Carbon-Zirconium-Hafnium), JPE 23, 218-235 (2002). doi:10.1361/105497102770331703

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-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); 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); 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_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}
}