Nd–O phases

10 phases (tier A 4, tier C 3, liquid 1, gas 2); 7 stable in a calculated diagram. Structure types are assigned only when the stored evidence supports an assignment under the stated tier rules (tier A: standard phase name; tier B: unique Materials Project + OQMD on-hull match, DFT-supported; tier C: one structure stated by the assessment's crystallographic table, assessor-stated); other phases list candidates and are marked needs_review. Stability is from phase diagrams calculated with pycalphad from the SGTE binary collection (evidence class: model).

Data: interactive registry · full JSON · Nd–O system page · Markdown · field reference

Phases of the Nd–O system (10)
Phase	Structure	Basis	Stability (calculated)	TDB models
BCC_A2 phase:nd-o:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 1128–1305.26 K, x(O) 0–0.01477	2
A_R2O3_D52 phase:nd-o:d52-a-r2o3	A-La2O3 · D5_2 · hP5 · P-3m1 (164)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 2 of 2 calculated diagram(s): 300–2172.76 K, x(O) 0.6–0.6	2
DHCP phase:nd-o:dhcp-a3	alpha-La · A3' · hP4 · P6_3/mmc (194)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–1135 K, x(O) 0–0.00786	2
FCC_A1 phase:nd-o:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
GAS phase:nd-o:gas	gas	gas	stable in 1 of 1 calculated diagram(s): 2485–2500 K, x(O) 1–1	1
H_R2O3 phase:nd-o:h-r2o3	H-La2O3 · hP10 · P6_3/mmc (194)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	not stable in 2 calculated diagram(s)	2
HCP_A3 phase:nd-o:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
ION phase:nd-o:ion	liquid	liquid	stable in 2 of 2 calculated diagram(s): 1264–2500 K, x(O) 0–0.57992	2
O2GAS phase:nd-o:o2gas	gas	gas	stable in 2 of 2 calculated diagram(s): 300–2500 K, x(O) 1–1	2
X_R2O3 phase:nd-o:r2o3-x	Nd2O3 · cI26 · Im-3m (229)	tier C: assessor-stated (Hallstedt 2025 crystallographic table)	stable in 2 of 2 calculated diagram(s): 2475–2500 K, x(O) 0.6–0.6	2

BCC_A2 (Nd–O)

Id: phase:nd-o:bcc-a2; status assigned
Structure: W · A2 · cI2 · Im-3m (229); type st:a2-w-ci2; tier A: standard phase name; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 1128–1305.26 K, x(O) 0–0.01477
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:bcc-a2
tdb: tdb:NdO-07Zin.tdb:BCC_A2, tdb:NdO-15Dot.tdb:BCC_A2

TDB models of BCC_A2 (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: BCC_A2, type code %B, sha256 0671e946c589d9b9…

42: PHASE BCC_A2 %B 2 1 3 !
43: CONST BCC_A2 : ND : VA : !

NdO-15Dot.tdb: BCC_A2, type code %B, sha256 cbc54824da87bc68…

41: PHASE BCC_A2 %B 2 1 3 !
42: CONST BCC_A2 : ND : O VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

A_R2O3_D52 (Nd–O)

Id: phase:nd-o:d52-a-r2o3; status assigned
Structure: A-La2O3 · D5_2 · hP5 · P-3m1 (164); type st:d5-2-a-la2o3-hp5; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (unrecognised_name_tokens:A,R2O3); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: stable in 2 of 2 calculated diagram(s): 300–2172.76 K, x(O) 0.6–0.6
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:d52-a-r2o3
tdb: tdb:NdO-07Zin.tdb:A_R2O3_D52, tdb:NdO-15Dot.tdb:A_R2O3_D52

TDB models of A_R2O3_D52 (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: A_R2O3_D52, type code %, sha256 0671e946c589d9b9…

57: PHASE A_R2O3_D52:I % 2 2 3 !
58: CONST A_R2O3_D52:I : ND+3 : O-2 : !

NdO-15Dot.tdb: A_R2O3_D52, type code %, sha256 cbc54824da87bc68…

56: PHASE A_R2O3_D52:I % 2 2 3 !
57: CONST A_R2O3_D52:I : ND+3 : O-2 : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

DHCP (Nd–O)

Id: phase:nd-o:dhcp-a3; status assigned
Structure: alpha-La · A3' · hP4 · P6_3/mmc (194); type st:a3-alpha-la-hp4; tier A: standard phase name; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–1135 K, x(O) 0–0.00786
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:dhcp-a3
tdb: tdb:NdO-07Zin.tdb:DHCP, tdb:NdO-15Dot.tdb:DHCP

TDB models of DHCP (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: DHCP, type code %, sha256 0671e946c589d9b9…

52: PHASE DHCP % 1 1 !
53: CONST DHCP : ND : !

NdO-15Dot.tdb: DHCP, type code %, sha256 cbc54824da87bc68…

51: PHASE DHCP % 2 1 0.5 !
52: CONST DHCP : ND : O VA% : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

FCC_A1 (Nd–O)

Id: phase:nd-o:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
Stoichiometry: Nd 1.0000
Stability: not stable in 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:fcc-a1
tdb: tdb:NdO-07Zin.tdb:FCC_A1, tdb:NdO-15Dot.tdb:FCC_A1

TDB models of FCC_A1 (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: FCC_A1, type code %A, sha256 0671e946c589d9b9…

37: PHASE FCC_A1 %A 2 1 1 !
38: CONST FCC_A1 : ND : VA : !

NdO-15Dot.tdb: FCC_A1, type code %A, sha256 cbc54824da87bc68…

36: PHASE FCC_A1 %A 2 1 1 !
37: CONST FCC_A1 : ND : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

GAS (Nd–O)

Id: phase:nd-o:gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 1 of 1 calculated diagram(s): 2485–2500 K, x(O) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (2): corpus: corpus:phase:nd-o:gas
tdb: tdb:NdO-15Dot.tdb:GAS

TDB models of GAS (1): PHASE and CONSTITUENT statements as written

NdO-15Dot.tdb: GAS, type code %, sha256 cbc54824da87bc68…

69: PHASE GAS:G % 1 1 !
70: CONST GAS:G : ND O O2% O3 : !

Example references (1 of 1; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase

H_R2O3 (Nd–O)

Id: phase:nd-o:h-r2o3; status assigned
Structure: H-La2O3 · hP10 · P6_3/mmc (194); type st:h-la2o3-hp10; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (name_has_descriptive_tokens:H,R2O3, no_structure_token); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: not stable in 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:h-r2o3
tdb: tdb:NdO-07Zin.tdb:H_R2O3, tdb:NdO-15Dot.tdb:H_R2O3

TDB models of H_R2O3 (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: H_R2O3, type code %, sha256 0671e946c589d9b9…

62: PHASE H_R2O3:I % 2 2 3 !
63: CONST H_R2O3:I : ND+3 : O-2 : !

NdO-15Dot.tdb: H_R2O3, type code %, sha256 cbc54824da87bc68…

61: PHASE H_R2O3:I % 2 2 3 !
62: CONST H_R2O3:I : ND+3 : O-2 : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

HCP_A3 (Nd–O)

Id: phase:nd-o:hcp-a3; status assigned
Structure: Mg · A3 · hP2 · P6_3/mmc (194); type st:a3-mg-hp2; tier A: standard phase name; confidence high
Stoichiometry: Nd 1.0000
Stability: not stable in 2 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:hcp-a3
tdb: tdb:NdO-07Zin.tdb:HCP_A3, tdb:NdO-15Dot.tdb:HCP_A3

TDB models of HCP_A3 (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: HCP_A3, type code %A, sha256 0671e946c589d9b9…

47: PHASE HCP_A3 %A 2 1 0.5 !
48: CONST HCP_A3 : ND : VA : !

NdO-15Dot.tdb: HCP_A3, type code %A, sha256 cbc54824da87bc68…

46: PHASE HCP_A3 %A 2 1 0.5 !
47: CONST HCP_A3 : ND : VA : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

ION (Nd–O)

Id: phase:nd-o:ion; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 1264–2500 K, x(O) 0–0.57992
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:ion
tdb: tdb:NdO-07Zin.tdb:ION, tdb:NdO-15Dot.tdb:ION

TDB models of ION (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: ION, type code %, sha256 0671e946c589d9b9…

32: PHASE ION:Y % 2 1 1 !
33: CONST ION:Y : ND+3 : O-2 VA : !

NdO-15Dot.tdb: ION, type code %, sha256 cbc54824da87bc68…

31: PHASE ION:Y % 2 1 1 !
32: CONST ION:Y : ND+3 : O-2 VA O : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

O2GAS (Nd–O)

Id: phase:nd-o:o2gas; status assigned
Structure: gas; type st:gas; gas; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–2500 K, x(O) 1–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:o2gas
tdb: tdb:NdO-07Zin.tdb:O2GAS, tdb:NdO-15Dot.tdb:O2GAS

TDB models of O2GAS (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: O2GAS, type code %, sha256 0671e946c589d9b9…

70: PHASE O2GAS % 1 1 !
71: CONST O2GAS : O2 : !

NdO-15Dot.tdb: O2GAS, type code %, sha256 cbc54824da87bc68…

72: PHASE O2GAS % 1 1 !
73: CONST O2GAS : O2 : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

X_R2O3 (Nd–O)

Id: phase:nd-o:r2o3-x; status assigned
Structure: Nd2O3 · cI26 · Im-3m (229); type st:nd2o3-ci26; tier C: assessor-stated (Hallstedt 2025 crystallographic table); confidence assessor-stated
Structure source: B. Hallstedt, The SGTE collection of binary datasets, Calphad 89 (2025) 102833, supplementary crystallographic table (mmc2) doi:10.1016/j.calphad.2025.102833
Caveat: not certain from the name or DFT alone (name_has_descriptive_tokens:R2O3,X, no_structure_token); structure as stated in the SGTE crystallographic table for this phase name and system
Stability: stable in 2 of 2 calculated diagram(s): 2475–2500 K, x(O) 0.6–0.6
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:nd-o:r2o3-x
tdb: tdb:NdO-07Zin.tdb:X_R2O3, tdb:NdO-15Dot.tdb:X_R2O3

TDB models of X_R2O3 (2): PHASE and CONSTITUENT statements as written

NdO-07Zin.tdb: X_R2O3, type code %, sha256 0671e946c589d9b9…

67: PHASE X_R2O3:I % 2 2 3 !
68: CONST X_R2O3:I : ND+3 : O-2 : !

NdO-15Dot.tdb: X_R2O3, type code %, sha256 cbc54824da87bc68…

66: PHASE X_R2O3:I % 2 2 3 !
67: CONST X_R2O3:I : ND+3 : O-2 : !

Example references (2 of 2; assessments first):

doi:10.1016/j.jnucmat.2014.12.061 Giannina Dottavio, Yves Pontillon, Lionel Desgranges, Christine Guéneau, Renaud C. Belin, Characterising the U–Nd–O miscibility gap by an experimental and a theoretical approach, Journal of Nuclear Materials 458, 394-405 (2015).
assessment that models this phase
doi:10.1016/j.pmatsci.2006.09.002 M ZINKEVICH, Thermodynamics of rare earth sesquioxides, Progress in Materials Science 52, 597-647 (2007).
assessment that models this phase

Please cite

R. Arróyave, J. Saal, D. Shin, ORCHID-Registry: phase registry of binary systems (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23735970
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 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); the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work). 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_phase_registry_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Registry: phase registry of binary systems}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735970},
  url       = {https://doi.org/10.5281/zenodo.23735970},
  note      = {Version 1, machine-extracted}
}

@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}
}