C–Ta phases

7 phases (tier A 4, liquid 1, needs_review 1, interstitial_fcc_a1_compound 1); 6 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 · C–Ta system page · Markdown · field reference

Phases of the C–Ta system (7)
Phase	Structure	Basis	Stability (calculated)	Literature values	TDB models
DIAMOND_A4 phase:c-ta:a4-diamond	C (diamond) · A4 · cF8 · Fd-3m (227)	tier A: standard phase name	not stable in 3 calculated diagram(s)	0	3
GRAPHITE_A9 phase:c-ta:a9-graphite	C (graphite) · A9 · hP4 · P6_3/mmc (194)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 300–4000 K, x(C) 1–1	2	3
BCC_A2 phase:c-ta:bcc-a2	W · A2 · cI2 · Im-3m (229)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 300–3289.99 K, x(C) 0–0.08363	2	3
FCC_A1 phase:c-ta:fcc-a1	NaCl · B1 · cF8 · Fm-3m (225)	assigned	stable in 3 of 3 calculated diagram(s): 300–4000 K, x(C) 0.37866–0.5	6	3
HCP_A3 phase:c-ta:hcp-a3	Mg · A3 · hP2 · P6_3/mmc (194)	tier A: standard phase name	stable in 3 of 3 calculated diagram(s): 300–3635.99 K, x(C) 0.27446–0.33333	4	3
LIQUID phase:c-ta:liquid	liquid	liquid	stable in 3 of 3 calculated diagram(s): 3073.71–4000 K, x(C) 0–0.75326	8	3
TA4C3 phase:c-ta:ta4c3		needs_review	stable in 2 of 2 calculated diagram(s): 300–2442.8 K, x(C) 0.386–0.4	0	2

DIAMOND_A4 (C–Ta)

Id: phase:c-ta:a4-diamond; status assigned
Structure: C (diamond) · A4 · cF8 · Fd-3m (227); type st:a4-c-diamond-cf8; tier A: standard phase name; confidence high
Stoichiometry: C 1.0000
Stability: not stable in 3 calculated diagram(s)
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (4): corpus: corpus:phase:c-ta:a4-diamond
tdb: tdb:TaC-16Pan.tdb:DIAMOND_A4, tdb:TaC-17Zha.tdb:DIAMOND_A4, tdb:TaC-96Fri-LB.tdb:DIAMOND_A4

TDB models of DIAMOND_A4 (3): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: DIAMOND_A4, type code %, sha256 ca6090d1f360ccc3…

41: PHASE DIAMOND_A4 % 1 1 !
42: CONST DIAMOND_A4 : C : !

TaC-17Zha.tdb: DIAMOND_A4, type code %, sha256 3552b962491e2504…

42: PHASE DIAMOND_A4 % 1 1 !
43: CONST DIAMOND_A4 : C : !

TaC-96Fri-LB.tdb: DIAMOND_A4, type code %, sha256 1f785b985585aadd…

53: PHASE DIAMOND_A4 % 1 1 !
54: CONST DIAMOND_A4 : C : !

Example references (3 of 3; assessments first):

doi:10.1016/0925-8388(96)02197-4 K. Frisk, A. Fernández Guillermet, Gibbs energy coupling of the phase diagram and thermochemistry in the tantalum-carbon system, Journal of Alloys and Compounds 238, 167-179 (1996).
assessment that models this phase
doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
assessment that models this phase

GRAPHITE_A9 (C–Ta)

Id: phase:c-ta:a9-graphite; status assigned
Structure: C (graphite) · A9 · hP4 · P6_3/mmc (194); type st:a9-c-graphite-hp4; tier A: standard phase name; confidence high
Stoichiometry: C 1.0000
Stability: stable in 3 of 3 calculated diagram(s): 300–4000 K, x(C) 1–1
Literature: 2 values (2 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:c-ta:a9-graphite
paper: paper:10.1016/0925-8388(96)02197-4:gr
tdb: tdb:TaC-16Pan.tdb:GRAPHITE_A9, tdb:TaC-17Zha.tdb:GRAPHITE_A9, tdb:TaC-96Fri-LB.tdb:GRAPHITE_A9

TDB models of GRAPHITE_A9 (3): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: GRAPHITE_A9, type code %, sha256 ca6090d1f360ccc3…

46: PHASE GRAPHITE_A9 % 1 1 !
47: CONST GRAPHITE_A9 : C : !

TaC-17Zha.tdb: GRAPHITE_A9, type code %, sha256 3552b962491e2504…

47: PHASE GRAPHITE_A9 % 1 1 !
48: CONST GRAPHITE_A9 : C : !

TaC-96Fri-LB.tdb: GRAPHITE_A9, type code %, sha256 1f785b985585aadd…

58: PHASE GRAPHITE_A9 % 1 1 !
59: CONST GRAPHITE_A9 : C : !

Example references (3 of 3; assessments first):

doi:10.1016/0925-8388(96)02197-4 K. Frisk, A. Fernández Guillermet, Gibbs energy coupling of the phase diagram and thermochemistry in the tantalum-carbon system, Journal of Alloys and Compounds 238, 167-179 (1996).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
assessment that models this phase

BCC_A2 (C–Ta)

Id: phase:c-ta: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 3 of 3 calculated diagram(s): 300–3289.99 K, x(C) 0–0.08363
Literature: 2 values (2 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:c-ta:bcc-a2
paper: paper:10.1016/0925-8388(96)02197-4:B.c.c.
tdb: tdb:TaC-16Pan.tdb:BCC_A2, tdb:TaC-17Zha.tdb:BCC_A2, tdb:TaC-96Fri-LB.tdb:BCC_A2

TDB models of BCC_A2 (3): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: BCC_A2, type code %B, sha256 ca6090d1f360ccc3…

31: PHASE BCC_A2 %B 2 1 3 !
32: CONST BCC_A2 : TA : C VA% : !

TaC-17Zha.tdb: BCC_A2, type code %B, sha256 3552b962491e2504…

32: PHASE BCC_A2 %B 2 1 3 !
33: CONST BCC_A2 : TA : C VA% : !

TaC-96Fri-LB.tdb: BCC_A2, type code %B, sha256 1f785b985585aadd…

43: PHASE BCC_A2 %B 2 1 3 !
44: CONST BCC_A2 : TA : C VA% : !

Example references (3 of 3; assessments first):

doi:10.1016/0925-8388(96)02197-4 K. Frisk, A. Fernández Guillermet, Gibbs energy coupling of the phase diagram and thermochemistry in the tantalum-carbon system, Journal of Alloys and Compounds 238, 167-179 (1996).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
assessment that models this phase

FCC_A1 (C–Ta)

Id: phase:c-ta:fcc-a1; status assigned
Structure: NaCl · B1 · cF8 · Fm-3m (225); type st:b1-nacl-cf8; interstitial_fcc_a1_compound; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 300–4000 K, x(C) 0.37866–0.5
Literature: 6 values (6 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:c-ta:fcc-a1
paper: paper:10.1016/0925-8388(96)02197-4:TaC
tdb: tdb:TaC-16Pan.tdb:FCC_A1, tdb:TaC-17Zha.tdb:FCC_A1, tdb:TaC-96Fri-LB.tdb:FCC_A1

TDB models of FCC_A1 (3): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: FCC_A1, type code %A, sha256 ca6090d1f360ccc3…

26: PHASE FCC_A1 %A 2 1 1 !
27: CONST FCC_A1 : TA : C% VA : !

TaC-17Zha.tdb: FCC_A1, type code %A, sha256 3552b962491e2504…

27: PHASE FCC_A1 %A 2 1 1 !
28: CONST FCC_A1 : TA : C% VA : !

TaC-96Fri-LB.tdb: FCC_A1, type code %A, sha256 1f785b985585aadd…

38: PHASE FCC_A1 %A 2 1 1 !
39: CONST FCC_A1 : TA : C% VA : !

Example references (3 of 3; assessments first):

doi:10.1016/0925-8388(96)02197-4 K. Frisk, A. Fernández Guillermet, Gibbs energy coupling of the phase diagram and thermochemistry in the tantalum-carbon system, Journal of Alloys and Compounds 238, 167-179 (1996).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
assessment that models this phase

HCP_A3 (C–Ta)

Id: phase:c-ta: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: stable in 3 of 3 calculated diagram(s): 300–3635.99 K, x(C) 0.27446–0.33333
Literature: 4 values (4 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:c-ta:hcp-a3
paper: paper:10.1016/0925-8388(96)02197-4:Ta2C
tdb: tdb:TaC-16Pan.tdb:HCP_A3, tdb:TaC-17Zha.tdb:HCP_A3, tdb:TaC-96Fri-LB.tdb:HCP_A3

TDB models of HCP_A3 (3): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: HCP_A3, type code %A, sha256 ca6090d1f360ccc3…

36: PHASE HCP_A3 %A 2 1 0.5 !
37: CONST HCP_A3 : TA : C% VA : !

TaC-17Zha.tdb: HCP_A3, type code %A, sha256 3552b962491e2504…

37: PHASE HCP_A3 %A 2 1 0.5 !
38: CONST HCP_A3 : TA : C% VA : !

TaC-96Fri-LB.tdb: HCP_A3, type code %A, sha256 1f785b985585aadd…

48: PHASE HCP_A3 %A 2 1 0.5 !
49: CONST HCP_A3 : TA : C% VA : !

Example references (3 of 3; assessments first):

doi:10.1016/0925-8388(96)02197-4 K. Frisk, A. Fernández Guillermet, Gibbs energy coupling of the phase diagram and thermochemistry in the tantalum-carbon system, Journal of Alloys and Compounds 238, 167-179 (1996).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
assessment that models this phase

LIQUID (C–Ta)

Id: phase:c-ta:liquid; status assigned
Structure: liquid; type st:liquid; liquid; confidence high
Stability: stable in 3 of 3 calculated diagram(s): 3073.71–4000 K, x(C) 0–0.75326
Literature: 8 values (8 accepted) from 1 papers
Interactive: phase registry entry

Names (5): corpus: corpus:phase:c-ta:liquid
paper: paper:10.1016/0925-8388(96)02197-4:L
tdb: tdb:TaC-16Pan.tdb:LIQUID, tdb:TaC-17Zha.tdb:LIQUID, tdb:TaC-96Fri-LB.tdb:LIQUID

TDB models of LIQUID (3): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: LIQUID, type code %, sha256 ca6090d1f360ccc3…

21: PHASE LIQUID:L % 1 1 !
22: CONST LIQUID:L : C TA : !

TaC-17Zha.tdb: LIQUID, type code %, sha256 3552b962491e2504…

22: PHASE LIQUID:L % 1 1 !
23: CONST LIQUID:L : C TA : !

TaC-96Fri-LB.tdb: LIQUID, type code %, sha256 1f785b985585aadd…

33: PHASE LIQUID:L % 1 1 !
34: CONST LIQUID:L : C TA : !

Example references (3 of 3; assessments first):

doi:10.1016/0925-8388(96)02197-4 K. Frisk, A. Fernández Guillermet, Gibbs energy coupling of the phase diagram and thermochemistry in the tantalum-carbon system, Journal of Alloys and Compounds 238, 167-179 (1996).
assessment that models this phase; reports values for this phase
doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
assessment that models this phase

TA4C3 (C–Ta)

Id: phase:c-ta:ta4c3; status needs_review
No structure assigned. Why: assessment_declared_blocked_by:models_disagree_on_composition; models_disagree_on_composition; no_structure_token
Candidate (sgte_mmc2): In3Te4 · hR7 · R-3m (166) — Hallstedt 2025 mmc2 row for TA4C3: Ta4C3
Candidate (sgte_mmc2): In3Te4 · hR7 · R-3m (166) — Hallstedt 2025 mmc2 row for TA4C3: Ta4C3 (or rather Ta3C2)
Candidate (tdb_comment): In3Te4 · hR7 · R-3m — TaC-16Pan.tdb: 'Prototype In3Te4 (hR7, R-3m)'
Candidate (tdb_comment): In3Te4 · hR7 · R-3m — TaC-17Zha.tdb: 'Prototype In3Te4 (hR7, R-3m)'
Stability: stable in 2 of 2 calculated diagram(s): 300–2442.8 K, x(C) 0.386–0.4
Literature: 0 values (0 accepted) from 0 papers
Interactive: phase registry entry

Names (3): corpus: corpus:phase:c-ta:ta4c3
tdb: tdb:TaC-16Pan.tdb:TA4C3, tdb:TaC-17Zha.tdb:TA4C3

TDB models of TA4C3 (2): PHASE and CONSTITUENT statements as written

TaC-16Pan.tdb: TA4C3, type code %, sha256 ca6090d1f360ccc3…

51: PHASE TA4C3 % 2 0.614 0.386 !
52: CONST TA4C3 : TA : C : !

TaC-17Zha.tdb: TA4C3, type code %, sha256 3552b962491e2504…

52: PHASE TA4C3 % 2 3 2 !
53: CONST TA4C3 : TA : C : !

Example references (2 of 2; assessments first):

doi:10.1016/j.calphad.2016.02.001 Y. Pan, P. Zhou, Y. Peng, Y. Du, F. Luo, Calphad, 53, 1-9(2016).
assessment that models this phase
doi:10.1016/j.calphad.2017.09.003 C. Zhang, H. Yin, Y. Du, Y. Pan, P. Deng, Calphad, 59, 99-1069(2017).
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}
}