Ho–O system

28 accepted literature values from 1 paper(s) (experimental 11, model 17); 1 calculated phase diagram(s).

Data: JSON · CSV · interactive explorer · interactive phase diagram · phases (7) · papers (bibliography) · Markdown

Accepted values by evidence class
Evidence class	Values
experimental	11
model	17

Accepted values by property group
Property group	Values
phase transition	11
formation	1
heat capacity / entropy / enthalpy	8
crystal structure	3
other property	5

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
HoO-23Nak.tdb	R. Nakazawa, A. Itoh, S. Yasui, M. Kurata, Y. Kobayashi, Calphad, 83, 102636(2023). doi:10.1016/j.calphad.2023.102636	`b0048ff0f3c67c3606de039964163398ae7322c2793c699c29ccc0df99198ab5`	viewer · TDB · JSON

Convex hulls: Materials Project DFT hull · OQMD DFT hull

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, Ho–O system (1)
Phase	Compound	Value	T (K)	Class	MP DFT (kJ/mol-atom)	OQMD DFT (kJ/mol-atom)	Source	Location	Quote
C-Ho2O3	Ho2O3	-376.66 kJ/mol-atom	298.15	model	-389.188 (mp-aaaaabfg)	-373.796 (oqmd-5389)	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 29 report

Other properties

Phase transition (11)

Phase transition, Ho–O system
Property	Value	T (K)	Phases / composition	Class	Source	Location
Phase transition	1273 K	1273	polymorphic: C ⇒ B alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Hoekstra 1966	Table 2.3, p. 10, row 22 report
Phase transition	2453 K	2453	polymorphic: B ⇔ H alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Coutures 1976	Table 2.1, p. 7, row 22 report
Phase transition	2453 K	2453	polymorphic: C ⇔ B alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Coutures 1976	Table 2.1, p. 7, row 21 report
Phase transition	2453 K	2453	polymorphic: C ⇔ B alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Foex 1966	Table 2.1, p. 7, row 19 report
Phase transition	2458 K	2458	polymorphic: C <=> B alloy: Ho 0.4, O 0.6	model	[1] ZINKEVICH 2007	Table 2.2, p. 8, row 6 report
Phase transition	2463 K	2463	polymorphic: C ⇔ B alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Tresvyatkii 1971	Table 2.1, p. 7, row 23 report
Phase transition	2463 K	2463	polymorphic: C ⇔ B alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Shevtchenko 1985	Table 2.1, p. 7, row 25 report
Phase transition	2473 K	2473	polymorphic: B ⇔ H alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Shevtchenko 1985	Table 2.1, p. 7, row 26 report
Phase transition	2483 K	2483	polymorphic: B <=> H alloy: Ho 0.4, O 0.6	model	[1] ZINKEVICH 2007	Table 2.2, p. 8, row 19 report
Phase transition	2493 K	2493	polymorphic: B ⇔ H alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Tresvyatkii 1971	Table 2.1, p. 7, row 24 report
Phase transition	2513 K	2513	polymorphic: B ⇔ H alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Foex 1966	Table 2.1, p. 7, row 20 report

Heat capacity / entropy / enthalpy (8)

Heat capacity / entropy / enthalpy, Ho–O system
Property	Value	T (K)	Phases / composition	Class	Source	Location
Entropy printed: Δtrs°S	22.537 unknown		C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 34 report
Entropy printed: Δtrs°S	5.451 unknown		C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 33 report
Entropy printed: ΔS	4.522 J mol−1 K−1		Ho2O3 alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Hoekstra 1966	Table 5.1, p. 18, row 18 report
Entropy printed: ΔS	4.522 J mol^-1 K^-1		UNKNOWN alloy: Ho 0.4, O 0.6	experimental	[1] ZINKEVICH 2007 cites Hoekstra 1966	Table 5.1, p. 18, row 18 report
Entropy printed: °S	158.15 unknown	298.15	C-Ho₂O₃ alloy: Ho 0.4, O 0.6	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 29 report
Entropy printed: Δtrs°S	3.982 unknown	2458	C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 30 report
Entropy printed: Δtrs°S	13.986 unknown	2483	C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 31 report
Entropy printed: Δtrs°S	30.916 unknown	2688	C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 32 report

Crystal structure (3)

Crystal structure, Ho–O system
Property	Value	T (K)	Phases / composition	Class	Source	Location
lattice molar volume	40.491 cm3 mol-1	298.15	Ho2O3 (A-type) alloy: Ho 0.4, O 0.6	model	[1] ZINKEVICH 2007	Table 3.1, p. 12, row 13 report
lattice molar volume	41.204 cm3 mol-1	298.15	Ho2O3 (B-type) alloy: Ho 0.4, O 0.6	model	[1] ZINKEVICH 2007	Table 3.1, p. 12, row 13 report
lattice molar volume	44.91 cm3 mol-1	298.15	Ho2O3 (C-type) alloy: Ho 0.4, O 0.6	model	[1] ZINKEVICH 2007	Table 3.1, p. 12, row 13 report

Other property (5)

Other property, Ho–O system
Property	Value	T (K)	Phases / composition	Class	Source	Location
Transition enthalpy printed: Δtrs°H	56969 unknown		C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 34 report
Transition enthalpy printed: Δtrs°H	17131 unknown		C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 33 report
Transition enthalpy printed: Δtrs°H	9787 unknown	2458	C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 30 report
Transition enthalpy printed: Δtrs°H	34727 unknown	2483	C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 31 report
Transition enthalpy printed: Δtrs°H	83102 unknown	2688	C-Ho₂O₃	model	[1] ZINKEVICH 2007	Table 6.1, p. 25, row 32 report

Sources

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

M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007). doi:10.1016/j.pmatsci.2006.09.002

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}
}