Hf–O system

13 accepted literature values from 1 paper(s) (experimental 3, DFT 10); 2 calculated phase diagram(s). 10 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 (9) · papers (bibliography) · Markdown

Accepted values by evidence class
Evidence class	Values
experimental	3
DFT	10

Accepted values by property group
Property group	Values
phase transition	3
crystal structure	10

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
HfO-06Shi.tdb	D. Shin, R. Arroyave, Z.-K. Liu, Calphad, 30, 375-86(2006). doi:10.1016/j.calphad.2006.08.006	`c524a8de35394af930522dc2c7fa54ec237abe7e3257e889a92a96fc34333fe9`	viewer · TDB · JSON
HfO-06Wan.tdb	C. Wang, PhD Thesis, Stuttgart, 2006.	`54d88108dcb3dde716d231d5b0be71a7ca3bf047897b3503932d1c3149d1d229`	viewer · TDB · JSON

Calculated three-phase invariants (model, mole fraction of the second component)
TDB file	T (K)	Phases at the invariant
HfO-06Shi.tdb	3072.98	ION (x(O) 0.66667) + HFO2_C1 (x(O) 0.66667) + GAS (x(O) 1)
HfO-06Shi.tdb	2793	ION (x(O) 0.5074) + HFO2_C1 (x(O) 0.66667) + HFO2_TETR (x(O) 0.66667)
HfO-06Shi.tdb	2793	HFO2_TETR (x(O) 0.66667) + HFO2_C1 (x(O) 0.66667) + GAS (x(O) 1)
HfO-06Shi.tdb	2582.59	ION (x(O) 0.02533) + BCC_A2 (x(O) 0.04924) + HCP_A3 (x(O) 0.0805)
HfO-06Shi.tdb	2565.4	HCP_A3 (x(O) 0.20969) + ION (x(O) 0.35796) + HFO2_TETR (x(O) 0.66667)
HfO-06Shi.tdb	2100	HCP_A3 (x(O) 0.21325) + HFO2_MONO (x(O) 0.66667) + HFO2_TETR (x(O) 0.66667)
HfO-06Shi.tdb	2100	HFO2_TETR (x(O) 0.66667) + HFO2_MONO (x(O) 0.66667) + GAS (x(O) 1)
HfO-06Wan.tdb	3073.95	HFO2_C1 (x(O) 0.66661) + ION (x(O) 0.66667) + GAS (x(O) 1)
HfO-06Wan.tdb	2517.27	BCC_A2 (x(O) 0.029) + ION (x(O) 0.03615) + HCP_A3 (x(O) 0.07174)

Convex hulls: Materials Project DFT hull · OQMD DFT hull · CALPHAD hull HfO-06Wan

Other properties

Phase transition (3)

Phase transition, Hf–O system
Property	Value	T (K)	Phases / composition	Class	Source	Location	Quote
Phase transition	2100 K	2100	monoclinic → tetragonal	experimental	[1] Shin 2006	p. 8 report	transformation temperatures for monoclinic → tetragonal → cubic → liquid are 2100 K, 2793 K, and 3073 K, respectively.
Phase transition	2793 K	2793	tetragonal → cubic	experimental	[1] Shin 2006	p. 8 report	transformation temperatures for monoclinic → tetragonal → cubic → liquid are 2100 K, 2793 K, and 3073 K, respectively.
Phase transition	3073 K	3073	cubic → liquid	experimental	[1] Shin 2006	p. 8 report	transformation temperatures for monoclinic → tetragonal → cubic → liquid are 2100 K, 2793 K, and 3073 K, respectively.

Crystal structure (10)

Crystal structure, Hf–O system
Property	Value	Phases / composition	Class	Source	Location
Lattice a	5.135 Å	Monoclinic (HfO2) alloy: O 0.666667	DFT	[1] Shin 2006	Table 1, p. 3, row 6 report
Lattice a	3.225 Å	α-Hf (HfO0.5)	DFT	[1] Shin 2006	Table 1, p. 3, row 4 report
Lattice a	4.364 Å	β-Hf (HfO3)	DFT	[1] Shin 2006	Table 1, p. 3, row 5 report
Lattice b	5.194 Å	Monoclinic (HfO2) alloy: O 0.666667	DFT	[1] Shin 2006	Table 1, p. 3, row 6 report
Lattice b	3.225 Å	α-Hf (HfO0.5)	DFT	[1] Shin 2006	Table 1, p. 3, row 4 report
Lattice b	4.364 Å	β-Hf (HfO3)	DFT	[1] Shin 2006	Table 1, p. 3, row 5 report
Lattice c	5.314 Å	Monoclinic (HfO2) alloy: O 0.666667	DFT	[1] Shin 2006	Table 1, p. 3, row 6 report
Lattice c	5.15 Å	α-Hf (HfO0.5)	DFT	[1] Shin 2006	Table 1, p. 3, row 4 report
Lattice c	4.364 Å	β-Hf (HfO3)	DFT	[1] Shin 2006	Table 1, p. 3, row 5 report
lattice beta	99.56 °	Monoclinic (HfO2) alloy: O 0.666667	DFT	[1] Shin 2006	Table 1, p. 3, row 6 report

Sources

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

Dongwon Shin, Raymundo Arróyave, Zi-Kui Liu, Thermodynamic modeling of the Hf–Si–O system, Calphad 30, 375-386 (2006). doi:10.1016/j.calphad.2006.08.006

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}
}