Hf–Nb system

27 accepted literature values from 1 paper(s) (experimental 3, DFT 24); 2 calculated phase diagram(s). 4 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 (4) · papers (bibliography) · Markdown

Accepted values by evidence class
Evidence class	Values
experimental	3
DFT	24

Accepted values by property group
Property group	Values
formation	8
crystal structure	15
model expression	4

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
HfNb-02Gho.tdb	G. Ghosh, A. van de Walle, M. Asta, G.B. Olson, Calphad, 26, 491-511(2002). doi:10.1016/S0364-5916(02)80003-7	`82d3feb715cf22ea38b82c64a92f7e0aafdd86750c8000dbb14f7f330b186151`	viewer · TDB · JSON
HfNb-96Fer-LB.tdb	A. Fernandez Guillermet, J. Alloys Compd., 234, 111-18(1996). doi:10.1016/0925-8388(95)01973-1	`2282d630abb4fc7a259be59b8fad4d0c601294bc106daf30f90be4d674166d36`	viewer · TDB · JSON

Convex hulls: Materials Project DFT hull · OQMD DFT hull · CALPHAD hull HfNb-96Fer-LB

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, Hf–Nb system (8)
Phase	Value	Class	Source	Location
Hf3Nb	4.04 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 2 report
Hf3Nb	11.499 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 2 report
HfNb (B19)	-6.162 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 4 report
HfNb (B19)	8.757 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 4 report
HfNb (B8₁)	5.746 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 3 report
HfNb (B8₁)	20.666 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 3 report
HfNb3	2.979 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 5 report
HfNb3	25.358 kJ/mol (basis unstated)	DFT	[1] Ghosh 2002	Table 6, p. 11, row 5 report

Other properties

Crystal structure (15)

Crystal structure, Hf–Nb system
Property	Value	T (K)	Phases / composition	Class	Source	Location
Lattice a	3.4342 Å		BCC alloy: Nb 0	experimental	[1] Ghosh 2002 cites ref. 1963Ros	Table 1, p. 6, row 3 report
Lattice a	3.5121 Å	0	BCC alloy: Nb 0	DFT	[1] Ghosh 2002	Table 1, p. 6, row 1 report
Lattice a	4.4454 Å	0	FCC alloy: Nb 0	DFT	[1] Ghosh 2002	Table 1, p. 6, row 4 report
Lattice a	3.193 Å		HCP alloy: Nb 0	experimental	[1] Ghosh 2002 cites ref. 1963Ros	Table 1, p. 6, row 6 report
Lattice a	3.1866 Å	0	HCP alloy: Nb 0	DFT	[1] Ghosh 2002	Table 1, p. 6, row 5 report
Lattice a	4.3243 Å	0	Hf3Nb alloy: Nb 0.25	DFT	[1] Ghosh 2002	Table 7, p. 12, row 2 report
Lattice a	4.3761 Å	0	Hf3Nb alloy: Nb 0.25	DFT	[1] Ghosh 2002	Table 7, p. 12, row 1 report
Lattice a	4.8073 Å	0	HfNb alloy: Nb 0.5	DFT	[1] Ghosh 2002	Table 7, p. 12, row 3 report
Lattice a	3.9047 Å	0	HfNb3 alloy: Nb 0.75	DFT	[1] Ghosh 2002	Table 7, p. 12, row 4 report
Lattice a	4.2543 Å	0	HfNb3 alloy: Nb 0.75	DFT	[1] Ghosh 2002	Table 7, p. 12, row 5 report
Lattice c	5.0395 Å		HCP alloy: Nb 0	experimental	[1] Ghosh 2002 cites ref. 1963Ros	Table 1, p. 6, row 6 report
Lattice c	5.0296 Å	0	HCP alloy: Nb 0	DFT	[1] Ghosh 2002	Table 1, p. 6, row 5 report
Lattice c	8.9507 Å	0	Hf3Nb alloy: Nb 0.25	DFT	[1] Ghosh 2002	Table 7, p. 12, row 2 report
Lattice c	3.3818 Å	0	HfNb alloy: Nb 0.5	DFT	[1] Ghosh 2002	Table 7, p. 12, row 3 report
Lattice c	9.8884 Å	0	HfNb3 alloy: Nb 0.75	DFT	[1] Ghosh 2002	Table 7, p. 12, row 4 report

Model expression (4)

Model expression, Hf–Nb system
Property	Value	Phases / composition	Class	Source	Location
hm form expression term printed: ΔHf (b)	13.243 kJ/mol (basis unstated)	Hf3Nb (DO3) alloy: Nb 0.25	DFT	[1] Ghosh 2002	Table 5, p. 10, row 1 report
hm form expression term printed: ΔHf (a)	2.72 kJ/mol (basis unstated)	HfNb (B2) alloy: Nb 0.5	DFT	[1] Ghosh 2002	Table 5, p. 10, row 2 report
hm form expression term printed: ΔHf (a)	2.393 kJ/mol (basis unstated)	HfNb (B32) alloy: Nb 0.5	DFT	[1] Ghosh 2002	Table 5, p. 10, row 3 report
hm form expression term printed: ΔHf (b)	6.267 kJ/mol (basis unstated)	HfNb3 (DO3) alloy: Nb 0.75	DFT	[1] Ghosh 2002	Table 5, p. 10, row 4 report

Sources

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

G. Ghosh, A. van de Walle, M. Asta, G.B. Olson, Phase stability of the Hf-Nb system: From first-principles to CALPHAD, Calphad 26, 491-511 (2002). doi:10.1016/s0364-5916(02)80003-7

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}
}