Co–Ho system

35 accepted literature values from 1 paper(s) (experimental 17, model 18); 1 calculated phase diagram(s).

Data: JSON · CSV · interactive explorer · interactive phase diagram · phases (12) · papers (bibliography) · Markdown

Accepted values by evidence class
Evidence class	Values
experimental	17
model	18

Accepted values by property group
Property group	Values
invariant reaction	21
phase transition	11
formation	1
activity / EMF / Gibbs energy	2

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
CoHo-09Jin.tdb	S. Jin, J. Wang, L.G. Zhang, H.S. Liu, L.B. Liu, F. Zheng, Z.P. Jin, J. Alloys Compd., 477, 233-38(2009). doi:10.1016/j.jallcom.2008.10.062	`2530e3403cc340aadbf277f417c2618a37c3cb85d5af012ef13cfea1d0f18424`	viewer · TDB · JSON

Calculated three-phase invariants (model, mole fraction of the second component)
TDB file	T (K)	Phases at the invariant
CoHo-09Jin.tdb	1638.4	LIQUID (x(Ho) 0.20011) + CO7HO2 (x(Ho) 0.22222) + CO3HO (x(Ho) 0.25)
CoHo-09Jin.tdb	1638.4	LIQUID (x(Ho) 0.20011) + CO7HO2 (x(Ho) 0.22222) + CO3HO (x(Ho) 0.25)
CoHo-09Jin.tdb	1638.4	LIQUID (x(Ho) 0.20021) + CO7HO2 (x(Ho) 0.22222) + CO3HO (x(Ho) 0.25)
CoHo-09Jin.tdb	1623.67	FCC_A1 (x(Ho) 0) + LIQUID (x(Ho) 0.06173) + CO17HO2 (x(Ho) 0.10526)
CoHo-09Jin.tdb	1623.59	CO17HO2 (x(Ho) 0.10526) + CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.15486)
CoHo-09Jin.tdb	1623.59	CO17HO2 (x(Ho) 0.10526) + CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.15476)
CoHo-09Jin.tdb	1623.59	CO17HO2 (x(Ho) 0.10526) + CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.15437)
CoHo-09Jin.tdb	1623.59	CO17HO2 (x(Ho) 0.10526) + CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.15437)
CoHo-09Jin.tdb	1619.63	CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.17375) + CO7HO2 (x(Ho) 0.22222)
CoHo-09Jin.tdb	1619.63	CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.17374) + CO7HO2 (x(Ho) 0.22222)
CoHo-09Jin.tdb	1619.62	CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.17318) + CO7HO2 (x(Ho) 0.22222)
CoHo-09Jin.tdb	1619.62	CO5HO_D2D (x(Ho) 0.15385) + LIQUID (x(Ho) 0.17338) + CO7HO2 (x(Ho) 0.22222)
CoHo-09Jin.tdb	1604.05	CO3HO (x(Ho) 0.25) + CO2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.33357)
CoHo-09Jin.tdb	1604.05	CO3HO (x(Ho) 0.25) + LIQUID (x(Ho) 0.33329) + CO2HO_C15 (x(Ho) 0.33333)
CoHo-09Jin.tdb	1427.13	CO17HO2 (x(Ho) 0.10526) + CO5HO_D2D (x(Ho) 0.15385) + CO7HO2 (x(Ho) 0.22222)
CoHo-09Jin.tdb	1170.63	LIQUID (x(Ho) 0.74765) + COHO3_D011 (x(Ho) 0.75) + HCP_A3 (x(Ho) 1)
CoHo-09Jin.tdb	1170.63	LIQUID (x(Ho) 0.7476) + COHO3_D011 (x(Ho) 0.75) + HCP_A3 (x(Ho) 1)
CoHo-09Jin.tdb	1170.63	LIQUID (x(Ho) 0.74761) + COHO3_D011 (x(Ho) 0.75) + HCP_A3 (x(Ho) 1)
CoHo-09Jin.tdb	1170.63	LIQUID (x(Ho) 0.74768) + COHO3_D011 (x(Ho) 0.75) + HCP_A3 (x(Ho) 1)
CoHo-09Jin.tdb	1170.63	LIQUID (x(Ho) 0.74771) + COHO3_D011 (x(Ho) 0.75) + HCP_A3 (x(Ho) 1)
CoHo-09Jin.tdb	1062.27	LIQUID (x(Ho) 0.63117) + CO7HO12 (x(Ho) 0.63158) + COHO3_D011 (x(Ho) 0.75)
CoHo-09Jin.tdb	1062.27	LIQUID (x(Ho) 0.63114) + CO7HO12 (x(Ho) 0.63158) + COHO3_D011 (x(Ho) 0.75)
CoHo-09Jin.tdb	1062.27	LIQUID (x(Ho) 0.63136) + CO7HO12 (x(Ho) 0.63158) + COHO3_D011 (x(Ho) 0.75)
CoHo-09Jin.tdb	1059.98	CO2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.61407) + CO7HO12 (x(Ho) 0.63158)
CoHo-09Jin.tdb	1059.98	CO2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.61414) + CO7HO12 (x(Ho) 0.63158)
CoHo-09Jin.tdb	1059.98	CO2HO_C15 (x(Ho) 0.33333) + LIQUID (x(Ho) 0.61388) + CO7HO12 (x(Ho) 0.63158)
CoHo-09Jin.tdb	1032.1	CO2HO_C15 (x(Ho) 0.33333) + CO3HO4 (x(Ho) 0.57143) + CO7HO12 (x(Ho) 0.63158)
CoHo-09Jin.tdb	694.99	FCC_A1 (x(Ho) 0) + HCP_A3 (x(Ho) 0) + CO17HO2 (x(Ho) 0.10526)

Convex hulls: Materials Project DFT hull · OQMD DFT hull

Invariant reactions (literature)

Invariant reactions reported in the literature for the Co–Ho system (21)
T (K)	Reaction / phases	Compositions (mole fraction)	Class	Source	Location
1703	peritectic: L + BCC_A1 -> HCP_A3	L: Ho 0.98	model	[1] Jin 2009	Table 3, p. 4, row 1 report
1638	peritectic: L + Co3Ho -> Co2Ho7	Co3Ho: Ho 0.25; Co2Ho7: Ho 0.777778	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 16 report
1637	peritectic: L + Co3Ho -> Co2Ho7	L: Ho 0.2008; Co3Ho: Ho 0.25; Co2Ho7: Ho 0.777778	model	[1] Jin 2009	Table 3, p. 4, row 17 report
1628	peritectic: L + Co17Ho2 -> Co5.5Ho	Co17Ho2: Ho 0.105263; Co5.5Ho: Ho 0.153846	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 20 report
1623	peritectic: L + Co17Ho2 -> Co5.5Ho	L: Ho 0.1548; Co17Ho2: Ho 0.105263; Co5.5Ho: Ho 0.153846	model	[1] Jin 2009	Table 3, p. 4, row 21 report
1623	eutectic: L -> Co17Ho2 + FCC_A1	L: Ho 0.062; Co17Ho2: Ho 0.105263	model	[1] Jin 2009	Table 3, p. 4, row 27 report
1618	eutectic: L -> Co7Ho2 + Co5.5Ho	L: Ho 0.1738; Co7Ho2: Ho 0.222222; Co5.5Ho: Ho 0.153846	model	[1] Jin 2009	Table 3, p. 4, row 19 report
1618	eutectic: L -> Co17Ho2 + FCC_A1	L: Ho 0.07; Co17Ho2: Ho 0.105263	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 26 report
1613	eutectic: L -> Co7Ho2 + Co5.5Ho	L: Ho 0.19; Co7Ho2: Ho 0.222222; Co5.5Ho: Ho 0.153846	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 18 report
1603	peritectic: L + Co3Ho -> Co2Ho	Co3Ho: Ho 0.25; Co2Ho: Ho 0.333333	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 12 report
1601	peritectic: L + Co3Ho -> Co2Ho	L: Ho 0.3343; Co3Ho: Ho 0.25; Co2Ho: Ho 0.333333	model	[1] Jin 2009	Table 3, p. 4, row 13 report
1423	eutectoid: Co5.5Ho -> Co7Ho2 + Co17Ho2	Co5.5Ho: Ho 0.153846; Co7Ho2: Ho 0.222222; Co17Ho2: Ho 0.105263	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 22 report
1423	eutectoid: Co5.5Ho -> Co7Ho2 + Co17Ho2	Co5.5Ho: Ho 0.153846; Co7Ho2: Ho 0.222222; Co17Ho2: Ho 0.105263	model	[1] Jin 2009	Table 3, p. 4, row 23 report
1168	peritectic: L + HCP_A3 -> CoHo3	CoHo3: Ho 0.75	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 2 report
1162	peritectic: L + HCP_A3 -> CoHo3	L: Ho 0.7487; CoHo3: Ho 0.75	model	[1] Jin 2009	Table 3, p. 4, row 3 report
1055	eutectic: L -> CoHo3 + Co7Ho12	L: Ho 0.6322; CoHo3: Ho 0.75; Co7Ho12: Ho 0.631579	model	[1] Jin 2009	Table 3, p. 4, row 5 report
1053	eutectic: L -> Co7Ho12 + Co2Ho	L: Ho 0.615; Co7Ho12: Ho 0.631579; Co2Ho: Ho 0.333333	model	[1] Jin 2009	Table 3, p. 4, row 9 report
1048	eutectic: L -> Co7Ho12 + Co2Ho	L: Ho 0.6; Co7Ho12: Ho 0.631579; Co2Ho: Ho 0.333333	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 8 report
1043	eutectic: L -> CoHo3 + Co7Ho12	L: Ho 0.67; CoHo3: Ho 0.75; Co7Ho12: Ho 0.631579	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 4 report
1028	peritectoid: Co7Ho12 + Co2Ho -> Co3Ho4	Co7Ho12: Ho 0.631579; Co2Ho: Ho 0.333333; Co3Ho4: Ho 0.571429	model	[1] Jin 2009	Table 3, p. 4, row 11 report
1028	peritectoid: Co7Ho12 + Co2Ho -> Co3Ho4	Co7Ho12: Ho 0.631579; Co2Ho: Ho 0.333333; Co3Ho4: Ho 0.571429	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 10 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, Co–Ho system (1)
Phase	Compound	Value	T (K)	Class	MP DFT (kJ/mol-atom)	OQMD DFT (kJ/mol-atom)	Source	Location	Quote
CoHo3		-10.539 kJ/mol (basis unstated)	298.15	model			[1] Jin 2009	p. 5 report	Considering the similar chemical property between Ho and these RE, it can be concluded that the enthalpies of formation of CoHo3 at 298 K should be around -10,000 J mol-1 , which is compatible with the presently assessed value, -10,539 J mol-1 .

Other properties

Phase transition (11)

Phase transition, Co–Ho system
Property	Value	T (K)	Phases / composition	Class	Source	Location	Quote
Phase transition	1043 K	1043	L ↔ CoHo3 + Co7 Ho12	experimental	[1] Jin 2009	p. 3 report	Note here the temperatures of two reactions, L ↔ CoHo3 + Co7 Ho12 at 1055 K and L ↔ Co7 Ho12 at 1056 K, deviate about 12 K from the corresponding measured values, 1043 K and 1068 K respectively.
Phase transition	1055 K	1055	L ↔ CoHo3 + Co7 Ho12	model	[1] Jin 2009	p. 3 report	Note here the temperatures of two reactions, L ↔ CoHo3 + Co7 Ho12 at 1055 K and L ↔ Co7 Ho12 at 1056 K, deviate about 12 K from the corresponding measured values, 1043 K and 1068 K respectively.
Phase transition	1056 K	1056	L ↔ Co7 Ho12	model	[1] Jin 2009	p. 3 report	Note here the temperatures of two reactions, L ↔ CoHo3 + Co7 Ho12 at 1055 K and L ↔ Co7 Ho12 at 1056 K, deviate about 12 K from the corresponding measured values, 1043 K and 1068 K respectively.
Phase transition	1056 K	1056	congruent melting: L -> Co7Ho12 L: Ho 0.6316; Co7Ho12: Ho 0.631579	model	[1] Jin 2009	Table 3, p. 4, row 7 report
Phase transition	1068 K	1068	L ↔ Co7 Ho12	experimental	[1] Jin 2009	p. 3 report	Note here the temperatures of two reactions, L ↔ CoHo3 + Co7 Ho12 at 1055 K and L ↔ Co7 Ho12 at 1056 K, deviate about 12 K from the corresponding measured values, 1043 K and 1068 K respectively.
Phase transition	1068 K	1068	congruent melting: L -> Co7Ho12 L: Ho 0.631579; Co7Ho12: Ho 0.631579	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 6 report
Phase transition	1423.15 K	1423.15	other: Co5.5 Ho -> Co7 Ho2 + Co17 Ho2	experimental	[1] Jin 2009	p. 1 report	Co5.5 Ho is unstable at low temperature and decomposes into Co7 Ho2 and Co17 Ho2 at about 1150 ◦ C.
Phase transition	1643 K	1643	congruent melting: L -> Co17Ho2 L: Ho 0.105263; Co17Ho2: Ho 0.105263	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 24 report
Phase transition	1648 K	1648	congruent melting: L -> Co17Ho2 L: Ho 0.1053; Co17Ho2: Ho 0.105263	model	[1] Jin 2009	Table 3, p. 4, row 25 report
Phase transition	1661 K	1661	congruent melting: L -> Co3Ho L: Ho 0.25; Co3Ho: Ho 0.25	model	[1] Jin 2009	Table 3, p. 4, row 15 report
Phase transition	1663 K	1663	congruent melting: L -> Co3Ho L: Ho 0.25; Co3Ho: Ho 0.25	experimental	[1] Jin 2009 cites Buschow 1969 doi	Table 3, p. 4, row 14 report

Activity / EMF / Gibbs energy (2)

Activity / EMF / Gibbs energy, Co–Ho system
Property	Value	T (K)	Phases / composition	Class	Source	Location	Quote
Gibbs energy printed: Gibbs energy of formation	-11953 J mol-1	1081		model	[1] Jin 2009	p. 4 report	However, Gibbs energy of formation of CoHo3 at 1081 K obtained through EMF measurements is -31,275 J mol-1 , while the assessed value is -11,953 J mol-1 , the difference is noticeable.
Gibbs energy printed: Gibbs energy of formation	-31275 J mol-1	1081		experimental	[1] Jin 2009 cites Su 2003	p. 4 report	However, Gibbs energy of formation of CoHo3 at 1081 K obtained through EMF measurements is -31,275 J mol-1 , while the assessed value is -11,953 J mol-1 , the difference is noticeable.

Sources

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

S. Jin, J. Wang, L.G. Zhang, H.S. Liu, L.B. Liu, F. Zheng et al., Thermodynamic assessment of the Co–Ho binary system, Journal of Alloys and Compounds 477, 233-238 (2009). doi:10.1016/j.jallcom.2008.10.062

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}
}