# Se–Tl phases

> Se–Tl system: 9 phases (tier A 5, tier C 1, liquid 1, needs_review 2); 8 stable in a calculated diagram in the ORCHID phase registry, with names, structure type when the stored evidence supports an assignment under the stated tier rules, calculated stability, verbatim TDB PHASE/CONSTITUENT statements and example references.

HTML: https://data.orchid-project.org/phases/pages/SE-TL.html · Markdown: https://data.orchid-project.org/phases/pages/SE-TL.md

9 phases (tier A 5, tier C 1, liquid 1, needs_review 2); 8 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](https://orchid-project.org/phases/?q=SE-TL) · [full JSON](https://data.orchid-project.org/phases/systems/SE-TL.json) · [Se–Tl system page](https://data.orchid-project.org/systems/SE-TL.html) · [Markdown](https://data.orchid-project.org/phases/pages/SE-TL.md) · [field reference](https://data.orchid-project.org/phases/SCHEMA.md)

Table: Phases of the Se–Tl system (9)

| Phase | Structure | Basis | Stability (calculated) | Literature values | TDB models |
|---|---|---|---|---:|---:|
| [HEXAGONAL_A8](#phase-se-tl-a8-hexagonal); _phase:se-tl:a8-hexagonal_ | gamma-Se · A8 · hP3 · P3_121 (152) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–494 K, x(Se) 1–1 | 0 | 1 |
| [BCC_A2](#phase-se-tl-bcc-a2); _phase:se-tl:bcc-a2_ | W · A2 · cI2 · Im-3m (229) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 507–2499.5 K, x(Se) 0–0 | 0 | 1 |
| [FCC_A1](#phase-se-tl-fcc-a1); _phase:se-tl:fcc-a1_ | Cu · A1 · cF4 · Fm-3m (225) | tier A: standard phase name | not stable in 1 calculated diagram(s) | 0 | 1 |
| [HCP_A3](#phase-se-tl-hcp-a3); _phase:se-tl:hcp-a3_ | Mg · A3 · hP2 · P6_3/mmc (194) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–507 K, x(Se) 0–0 | 0 | 1 |
| [LIQUID](#phase-se-tl-liquid); _phase:se-tl:liquid_ | liquid | liquid | stable in 1 of 1 calculated diagram(s): 475.38–2500 K, x(Se) 0–1 | 0 | 1 |
| [TL2SE](#phase-se-tl-tl2se); _phase:se-tl:tl2se_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 300–519.76 K, x(Se) 0.33333–0.33333 | 1 | 1 |
| [TL5SE3](#phase-se-tl-tl5se3); _phase:se-tl:tl5se3_ | Tl5Se3 · tP32 · P4/n (85) | tier C: assessor-stated (Hallstedt 2025 crystallographic table) | stable in 1 of 1 calculated diagram(s): 300–653.07 K, x(Se) 0.33346–0.37218 | 0 | 1 |
| [TLSE_B37](#phase-se-tl-tlse-b37); _phase:se-tl:tlse-b37_ | TlSe-alpha · B37 · tI16 · I4/mcm (140) | tier A: standard phase name | stable in 1 of 1 calculated diagram(s): 300–465.66 K, x(Se) 0.5–0.5 | 0 | 1 |
| [TLSE_BETA](#phase-se-tl-tlse-beta); _phase:se-tl:tlse-beta_ |  | needs_review | stable in 1 of 1 calculated diagram(s): 465.66–618.36 K, x(Se) 0.5–0.5 | 0 | 1 |

## HEXAGONAL_A8 (Se–Tl)

- Id: `phase:se-tl:a8-hexagonal`; status `assigned`
- Structure: gamma-Se · A8 · hP3 · P3_121 (152); type `st:a8-gamma-se-hp3`; tier A: standard phase name; confidence high
- Stoichiometry: Se 1.0000
- Stability: stable in 1 of 1 calculated diagram(s): 300–494 K, x(Se) 1–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:a8-hexagonal)

Names (2): _corpus: _corpus:phase:se-tl:a8-hexagonal  
_tdb: _tdb:TlSe-00Roe-LB.tdb:HEXAGONAL_A8  


### TDB models of HEXAGONAL_A8 (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): HEXAGONAL_A8, type code %, sha256 `8323ab45605996cf…`

~~~~text
52: PHASE HEXAGONAL_A8 % 1 1 !
53: CONST HEXAGONAL_A8 : SE : !
~~~~

## BCC_A2 (Se–Tl)

- Id: `phase:se-tl:bcc-a2`; status `assigned`
- Structure: W · A2 · cI2 · Im-3m (229); type `st:a2-w-ci2`; tier A: standard phase name; confidence high
- Stoichiometry: Tl 1.0000
- Stability: stable in 1 of 1 calculated diagram(s): 507–2499.5 K, x(Se) 0–0
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:bcc-a2)

Names (2): _corpus: _corpus:phase:se-tl:bcc-a2  
_tdb: _tdb:TlSe-00Roe-LB.tdb:BCC_A2  


### TDB models of BCC_A2 (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): BCC_A2, type code %B, sha256 `8323ab45605996cf…`

~~~~text
42: PHASE BCC_A2 %B 2 1 3 !
43: CONST BCC_A2 : TL : VA : !
~~~~

## FCC_A1 (Se–Tl)

- Id: `phase:se-tl:fcc-a1`; status `assigned`
- Structure: Cu · A1 · cF4 · Fm-3m (225); type `st:a1-cu-cf4`; tier A: standard phase name; confidence high
- Stoichiometry: Tl 1.0000
- Stability: not stable in 1 calculated diagram(s)
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:fcc-a1)

Names (2): _corpus: _corpus:phase:se-tl:fcc-a1  
_tdb: _tdb:TlSe-00Roe-LB.tdb:FCC_A1  


### TDB models of FCC_A1 (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): FCC_A1, type code %A, sha256 `8323ab45605996cf…`

~~~~text
37: PHASE FCC_A1 %A 2 1 1 !
38: CONST FCC_A1 : TL : VA : !
~~~~

## HCP_A3 (Se–Tl)

- Id: `phase:se-tl: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: Tl 1.0000
- Stability: stable in 1 of 1 calculated diagram(s): 300–507 K, x(Se) 0–0
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:hcp-a3)

Names (2): _corpus: _corpus:phase:se-tl:hcp-a3  
_tdb: _tdb:TlSe-00Roe-LB.tdb:HCP_A3  


### TDB models of HCP_A3 (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): HCP_A3, type code %A, sha256 `8323ab45605996cf…`

~~~~text
47: PHASE HCP_A3 %A 2 1 0.5 !
48: CONST HCP_A3 : TL : VA : !
~~~~

## LIQUID (Se–Tl)

- Id: `phase:se-tl:liquid`; status `assigned`
- Structure: liquid; type `st:liquid`; liquid; confidence high
- Stability: stable in 1 of 1 calculated diagram(s): 475.38–2500 K, x(Se) 0–1
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:liquid)

Names (2): _corpus: _corpus:phase:se-tl:liquid  
_tdb: _tdb:TlSe-00Roe-LB.tdb:LIQUID  


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

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): LIQUID, type code %, sha256 `8323ab45605996cf…`

~~~~text
32: PHASE LIQUID:L % 1 1 !
33: CONST LIQUID:L : SE TL TL2SE : !
~~~~

## TL2SE (Se–Tl)

- Id: `phase:se-tl:tl2se`; status `needs_review`
- No structure assigned. Why: no_on_hull_entry_in_mp; no_structure_token; sgte_mmc2_row_incomplete
- Candidate (dft_oqmd): P3 (143) — on-hull OQMD Se1 Tl2 at x(TL)=0.6667
- Candidate (sgte_mmc2): (Tl2Se) — Hallstedt 2025 mmc2 row for TL2SE: Tl2Se
- Stoichiometry: Se 0.3333, Tl 0.6667
- Stability: stable in 1 of 1 calculated diagram(s): 300–519.76 K, x(Se) 0.33333–0.33333
- Literature: 1 values (1 accepted) from 1 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:tl2se)

Names (3): _corpus: _corpus:phase:se-tl:tl2se  
_paper: _paper:10.1016/s0966-9795(99)00068-0:Tl2Se  
_tdb: _tdb:TlSe-00Roe-LB.tdb:TL2SE  


### TDB models of TL2SE (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): TL2SE, type code %, sha256 `8323ab45605996cf…`

~~~~text
57: PHASE TL2SE % 2 2 1 !
58: CONST TL2SE : TL : SE : !
~~~~

Example references (1 of 1; assessments first): 

- [doi:10.1016/s0966-9795(99)00068-0](https://doi.org/10.1016/s0966-9795%2899%2900068-0) F. Römermann, Y. Feutelais, S.G. Fries, R. Blachnik, Phase diagram experimental investigation and thermodynamic assessment of the thallium–selenium system, Intermetallics 8, 53-65 (2000).  
_reports values for this phase_

## TL5SE3 (Se–Tl)

- Id: `phase:se-tl:tl5se3`; status `assigned`
- Structure: Tl5Se3 · tP32 · P4/n (85); type `st:tl5se3-tp32`; 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](https://doi.org/10.1016/j.calphad.2025.102833)
- Caveat: not certain from the name or DFT alone (no_structure_token, off_stoichiometric_model); structure as stated in the SGTE crystallographic table for this phase name and system
- Stability: stable in 1 of 1 calculated diagram(s): 300–653.07 K, x(Se) 0.33346–0.37218
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:tl5se3)

Names (2): _corpus: _corpus:phase:se-tl:tl5se3  
_tdb: _tdb:TlSe-00Roe-LB.tdb:TL5SE3  


### TDB models of TL5SE3 (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): TL5SE3, type code %, sha256 `8323ab45605996cf…`

~~~~text
62: PHASE TL5SE3 % 3 5 2 1 !
63: CONST TL5SE3 : TL : SE : SE TL : !
~~~~

## TLSE_B37 (Se–Tl)

- Id: `phase:se-tl:tlse-b37`; status `assigned`
- Structure: TlSe-alpha · B37 · tI16 · I4/mcm (140); type `st:b37-tlse-alpha-ti16`; tier A: standard phase name; confidence high
- Stoichiometry: Se 0.5000, Tl 0.5000
- Stability: stable in 1 of 1 calculated diagram(s): 300–465.66 K, x(Se) 0.5–0.5
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:tlse-b37)

Names (2): _corpus: _corpus:phase:se-tl:tlse-b37  
_tdb: _tdb:TlSe-00Roe-LB.tdb:TLSE_B37  


### TDB models of TLSE_B37 (1): PHASE and CONSTITUENT statements as written

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): TLSE_B37, type code %, sha256 `8323ab45605996cf…`

~~~~text
67: PHASE TLSE_B37 % 2 1 1 !
68: CONST TLSE_B37 : TL : SE : !
~~~~

## TLSE_BETA (Se–Tl)

- Id: `phase:se-tl:tlse-beta`; status `needs_review`
- No structure assigned. Why: no_structure_token; polymorph_family:other phases of this system have the same composition
- Candidate (dft_mp): I4/mcm (140) — on-hull MP TlSe at x(TL)=0.5000
- Candidate (sgte_mmc2): (TlSe-beta) — Hallstedt 2025 mmc2 row for TLSE_BETA: TlSe-beta
- Stoichiometry: Se 0.5000, Tl 0.5000
- Stability: stable in 1 of 1 calculated diagram(s): 465.66–618.36 K, x(Se) 0.5–0.5
- Literature: 0 values (0 accepted) from 0 papers
- Interactive: [phase registry entry](https://orchid-project.org/phases/#phase:se-tl:tlse-beta)

Names (2): _corpus: _corpus:phase:se-tl:tlse-beta  
_tdb: _tdb:TlSe-00Roe-LB.tdb:TLSE_BETA  


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

[TlSe-00Roe-LB.tdb](https://orchid-project.org/data/databases/sgte-binary/TlSe-00Roe-LB.tdb): TLSE_BETA, type code %, sha256 `8323ab45605996cf…`

~~~~text
72: PHASE TLSE_BETA % 2 1 1 !
73: CONST TLSE_BETA : TL : SE : !
~~~~

## Please cite

- R. Arróyave, J. Saal, D. Shin, ORCHID-Registry: phase registry of binary systems (version 2026.10; Version 1, machine-extracted), Zenodo (2026). https://doi.org/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). https://doi.org/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.

```bibtex
@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}
}
```

---

Derived data CC BY 4.0 ([licence](https://creativecommons.org/licenses/by/4.0/)): cite the ORCHID phase registry and the sources named on the page (TDB assessments, Hallstedt 2025, Materials Project, OQMD). TDB statements are quoted as written; parameter expressions are not reproduced. Field reference: [SCHEMA.md](https://data.orchid-project.org/phases/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt).