Np–U phases

9 phases (tier A 6, liquid 1, needs_review 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 · Np–U system page · Markdown · field reference

Phases of the Np–U system (9)
Phase	Structure	Basis	Stability (calculated)	TDB models
ORTHORHOMBIC_A20 phase:np-u:a20-orthorhombic	alpha-U · A20 · oC4 · Cmcm (63)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–942.02 K, x(U) 0.53691–1	2
TETRAG_AD phase:np-u:ad-tetrag	beta-Np · A_d · tP4 · P4/nmm (129)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 458.9–896.5 K, x(U) 0–0.26653	2
BCC_A2 phase:np-u:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 856.06–2542.99 K, x(U) 0–1	2
FCC_A1 phase:np-u:fcc-a1	Cu · A1 · cF4 · Fm-3m (225)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
HCP_A3 phase:np-u:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	not stable in 2 calculated diagram(s)	2
LIQUID phase:np-u:liquid	liquid	liquid	stable in 2 of 2 calculated diagram(s): 917.28–4000 K, x(U) 0–1	2
NPU_ZETA phase:np-u:npu-zeta		needs_review	stable in 2 of 2 calculated diagram(s): 300–946.63 K, x(U) 0.23414–0.71951	2
ORTHO_AC phase:np-u:ortho-ac	alpha-Np · A_c · oP8 · Pnma (62)	tier A: standard phase name	stable in 2 of 2 calculated diagram(s): 300–555.02 K, x(U) 0–0.1032	2
TETRAGONAL_U phase:np-u:u-tetragonal		needs_review	stable in 2 of 2 calculated diagram(s): 914.55–1048.82 K, x(U) 0.69334–1	2

ORTHORHOMBIC_A20 (Np–U)

Id: phase:np-u:a20-orthorhombic; status assigned
Structure: alpha-U · A20 · oC4 · Cmcm (63); type st:a20-alpha-u-oc4; tier A: standard phase name; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–942.02 K, x(U) 0.53691–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:a20-orthorhombic
tdb: tdb:NpU-10Kur.tdb:ORTHORHOMBIC_A20, tdb:NpU-18Xie.tdb:ORTHORHOMBIC_A20

TDB models of ORTHORHOMBIC_A20 (2): PHASE and CONSTITUENT statements as written

NpU-10Kur.tdb: ORTHORHOMBIC_A20, type code %, sha256 f85b49b94decbbee…

52: PHASE ORTHORHOMBIC_A20 % 1 1 !
53: CONST ORTHORHOMBIC_A20 : NP U% : !

NpU-18Xie.tdb: ORTHORHOMBIC_A20, type code %, sha256 1d2cc8e207135d92…

50: PHASE ORTHORHOMBIC_A20 % 1 1 !
51: CONST ORTHORHOMBIC_A20 : NP U% : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

TETRAG_AD (Np–U)

Id: phase:np-u:ad-tetrag; status assigned
Structure: beta-Np · A_d · tP4 · P4/nmm (129); type st:a-d-beta-np-tp4; tier A: standard phase name; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 458.9–896.5 K, x(U) 0–0.26653
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:ad-tetrag
tdb: tdb:NpU-10Kur.tdb:TETRAG_AD, tdb:NpU-18Xie.tdb:TETRAG_AD

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

NpU-10Kur.tdb: TETRAG_AD, type code %, sha256 f85b49b94decbbee…

47: PHASE TETRAG_AD % 1 1 !
48: CONST TETRAG_AD : NP% U : !

NpU-18Xie.tdb: TETRAG_AD, type code %, sha256 1d2cc8e207135d92…

45: PHASE TETRAG_AD % 1 1 !
46: CONST TETRAG_AD : NP% U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

BCC_A2 (Np–U)

Id: phase:np-u: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): 856.06–2542.99 K, x(U) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:bcc-a2
tdb: tdb:NpU-10Kur.tdb:BCC_A2, tdb:NpU-18Xie.tdb:BCC_A2

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

NpU-10Kur.tdb: BCC_A2, type code %B, sha256 f85b49b94decbbee…

32: PHASE BCC_A2 %B 2 1 3 !
33: CONST BCC_A2 : NP% U% : VA : !

NpU-18Xie.tdb: BCC_A2, type code %B, sha256 1d2cc8e207135d92…

30: PHASE BCC_A2 %B 2 1 3 !
31: CONST BCC_A2 : NP% U% : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

FCC_A1 (Np–U)

Id: phase:np-u:fcc-a1; status assigned
Structure: Cu · A1 · cF4 · Fm-3m (225); type st:a1-cu-cf4; tier A: standard phase name; confidence high
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:np-u:fcc-a1
tdb: tdb:NpU-10Kur.tdb:FCC_A1, tdb:NpU-18Xie.tdb:FCC_A1

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

NpU-10Kur.tdb: FCC_A1, type code %A, sha256 f85b49b94decbbee…

27: PHASE FCC_A1 %A 2 1 1 !
28: CONST FCC_A1 : NP U : VA : !

NpU-18Xie.tdb: FCC_A1, type code %A, sha256 1d2cc8e207135d92…

25: PHASE FCC_A1 %A 2 1 1 !
26: CONST FCC_A1 : NP U : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

HCP_A3 (Np–U)

Id: phase:np-u:hcp-a3; status assigned
Structure: Mg · A3 · hP2 · P6_3/mmc (194); type st:a3-mg-hp2; tier A: standard phase name; confidence high
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:np-u:hcp-a3
tdb: tdb:NpU-10Kur.tdb:HCP_A3, tdb:NpU-18Xie.tdb:HCP_A3

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

NpU-10Kur.tdb: HCP_A3, type code %A, sha256 f85b49b94decbbee…

37: PHASE HCP_A3 %A 2 1 0.5 !
38: CONST HCP_A3 : NP U : VA : !

NpU-18Xie.tdb: HCP_A3, type code %A, sha256 1d2cc8e207135d92…

35: PHASE HCP_A3 %A 2 1 0.5 !
36: CONST HCP_A3 : NP U : VA : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

LIQUID (Np–U)

Id: phase:np-u:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 917.28–4000 K, x(U) 0–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:liquid
tdb: tdb:NpU-10Kur.tdb:LIQUID, tdb:NpU-18Xie.tdb:LIQUID

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

NpU-10Kur.tdb: LIQUID, type code %, sha256 f85b49b94decbbee…

22: PHASE LIQUID:L % 1 1 !
23: CONST LIQUID:L : NP U : !

NpU-18Xie.tdb: LIQUID, type code %, sha256 1d2cc8e207135d92…

20: PHASE LIQUID:L % 1 1 !
21: CONST LIQUID:L : NP U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

NPU_ZETA (Np–U)

Id: phase:np-u:npu-zeta; status needs_review
No structure assigned. Why: no_structure_token; off_stoichiometric_model
Candidate (sgte_mmc2): PuU-zeta · hR58 · R-3m (166) — Hallstedt 2025 mmc2 row for NPU_ZETA: NpU-zeta
Candidate (tdb_comment): PuU-zeta · hR58 · R-3m — NpU-10Kur.tdb: 'Prototype PuU-zeta (hR58, R-3m)'
Candidate (tdb_comment): PuU-zeta · hR58 · R-3m — NpU-18Xie.tdb: 'Prototype PuU-zeta (hR58, R-3m)'
Stability: stable in 2 of 2 calculated diagram(s): 300–946.63 K, x(U) 0.23414–0.71951
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:npu-zeta
tdb: tdb:NpU-10Kur.tdb:NPU_ZETA, tdb:NpU-18Xie.tdb:NPU_ZETA

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

NpU-10Kur.tdb: NPU_ZETA, type code %, sha256 f85b49b94decbbee…

62: PHASE NPU_ZETA % 1 1 !
63: CONST NPU_ZETA : NP U : !

NpU-18Xie.tdb: NPU_ZETA, type code %, sha256 1d2cc8e207135d92…

60: PHASE NPU_ZETA % 2 1 2 !
61: CONST NPU_ZETA : NP U : NP U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

ORTHO_AC (Np–U)

Id: phase:np-u:ortho-ac; status assigned
Structure: alpha-Np · A_c · oP8 · Pnma (62); type st:a-c-alpha-np-op8; tier A: standard phase name; confidence high
Stability: stable in 2 of 2 calculated diagram(s): 300–555.02 K, x(U) 0–0.1032
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:ortho-ac
tdb: tdb:NpU-10Kur.tdb:ORTHO_AC, tdb:NpU-18Xie.tdb:ORTHO_AC

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

NpU-10Kur.tdb: ORTHO_AC, type code %, sha256 f85b49b94decbbee…

42: PHASE ORTHO_AC % 1 1 !
43: CONST ORTHO_AC : NP% U : !

NpU-18Xie.tdb: ORTHO_AC, type code %, sha256 1d2cc8e207135d92…

40: PHASE ORTHO_AC % 1 1 !
41: CONST ORTHO_AC : NP% U : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
assessment that models this phase

TETRAGONAL_U (Np–U)

Id: phase:np-u:u-tetragonal; status needs_review
No structure assigned. Why: name_has_descriptive_tokens:TETRAGONAL; no_structure_token
Candidate (sgte_mmc2): beta-U · A_b · tP30 · P4_2/mnm (136) — Hallstedt 2025 mmc2 row for TETRAGONAL_U: beta-U
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — NpU-10Kur.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Candidate (tdb_comment): beta-U · tP30 · P4_2/mnm, SB: A_b — NpU-18Xie.tdb: 'Prototype beta-U (tP30, P4_2/mnm, SB: A_b)'
Stability: stable in 2 of 2 calculated diagram(s): 914.55–1048.82 K, x(U) 0.69334–1
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:np-u:u-tetragonal
tdb: tdb:NpU-10Kur.tdb:TETRAGONAL_U, tdb:NpU-18Xie.tdb:TETRAGONAL_U

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

NpU-10Kur.tdb: TETRAGONAL_U, type code %, sha256 f85b49b94decbbee…

57: PHASE TETRAGONAL_U % 1 1 !
58: CONST TETRAGONAL_U : NP U% : !

NpU-18Xie.tdb: TETRAGONAL_U, type code %, sha256 1d2cc8e207135d92…

55: PHASE TETRAGONAL_U % 1 1 !
56: CONST TETRAGONAL_U : NP U% : !

Example references (1 of 1; assessments first):

doi:10.1016/j.commatsci.2017.11.042 Wei Xie, Dane Morgan, CALPHAD modeling and ab initio calculations of the Np-U-Zr system, Computational Materials Science 143, 505-514 (2018).
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}
}