# Bi–K system

> Bi–K system: 83 accepted literature values (formation 50, invariant reaction 32, phase transition 1) and 3 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

HTML: https://data.orchid-project.org/systems/BI-K.html · Markdown: https://data.orchid-project.org/systems/BI-K.md

83 accepted literature values from 1 paper(s) (experimental 38, model 39, unspecified 6); 3 calculated phase diagram(s).

Data: [JSON](https://data.orchid-project.org/literature/systems/BI-K.json) · [CSV](https://data.orchid-project.org/systems/BI-K.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#BI-K) · [interactive phase diagram](https://orchid-project.org/phase-diagrams/#BI-K/BiK-12Niu.json) · [phases (10)](https://data.orchid-project.org/phases/pages/BI-K.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/BI-K.html) · [Markdown](https://data.orchid-project.org/systems/BI-K.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 38 |
| model | 39 |
| unspecified | 6 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 32 |
| phase transition | 1 |
| formation | 50 |

## 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.

Table: Assessments with a calculated phase diagram

| TDB file | Assessment | SHA-256 | Links |
|---|---|---|---|
| BiK-12Niu.tdb | C. Niu, C. Li, Z. Du, C. Guo, M. Liu, Thermochim. Acta, 528, 9-14(2012). [doi:10.1016/j.tca.2011.10.032](https://doi.org/10.1016/j.tca.2011.10.032) | `3ce72b86413e842a4b31807019480e25cd7d65498e3056723646ddd7b0657bb0` | [viewer](https://orchid-project.org/phase-diagrams/#BI-K/BiK-12Niu.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/BiK-12Niu.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/BiK-12Niu.json) |
| BiK-15Gie.tdb | W. Gierlotka, Thermochim. Acta, 604, 137-39(2015). [doi:10.1016/j.tca.2014.12.006](https://doi.org/10.1016/j.tca.2014.12.006) | `530ca2f96b764f0e938e0492dc7d217c044b6464c564309468b1a3eca67e5471` | [viewer](https://orchid-project.org/phase-diagrams/#BI-K/BiK-15Gie.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/BiK-15Gie.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/BiK-15Gie.json) |
| BiK-80Che-LB.tdb | P.-Y. Chevalier, unpublished work, 1980. | `e6d765540ed2fd20d6c43b22ade8397fd6c663863ea559f805a1fc83a68e529f` | [viewer](https://orchid-project.org/phase-diagrams/#BI-K/BiK-80Che-LB.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/BiK-80Che-LB.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/BiK-80Che-LB.json) |

Table: Calculated three-phase invariants (model, mole fraction of the second component)

| TDB file | T (K) | Phases at the invariant |
|---|---:|---|
| BiK-12Niu.tdb | 715.05 | BI2K3 (x(K) 0.6) + LIQUID (x(K) 0.60165) + BIK3_D03 (x(K) 0.75) |
| BiK-12Niu.tdb | 654.07 | LIQUID (x(K) 0.52549) + BI4K5 (x(K) 0.55556) + BI2K3 (x(K) 0.6) |
| BiK-12Niu.tdb | 626.92 | BI2K_C15 (x(K) 0.33333) + LIQUID (x(K) 0.49914) + BI4K5 (x(K) 0.55556) |
| BiK-12Niu.tdb | 553 | BIK3_D021 (x(K) 0.75) + BIK3_D03 (x(K) 0.75) + LIQUID (x(K) 0.99856) |
| BiK-12Niu.tdb | 553 | BI2K3 (x(K) 0.6) + BIK3_D021 (x(K) 0.75) + BIK3_D03 (x(K) 0.75) |
| BiK-12Niu.tdb | 538.41 | RHOMBOHEDRAL_A7 (x(K) 0) + LIQUID (x(K) 0.02594) + BI2K_C15 (x(K) 0.33333) |
| BiK-12Niu.tdb | 336.53 | BIK3_D021 (x(K) 0.75) + BCC_A2 (x(K) 1) + LIQUID (x(K) 1) |
| BiK-15Gie.tdb | 709.42 | LIQUID (x(K) 0.59659) + BI2K3 (x(K) 0.6) + BIK3_D03 (x(K) 0.75) |
| BiK-15Gie.tdb | 656.4 | LIQUID (x(K) 0.53702) + BI4K5 (x(K) 0.55556) + BI2K3 (x(K) 0.6) |
| BiK-15Gie.tdb | 636.51 | BI2K_C15 (x(K) 0.33333) + LIQUID (x(K) 0.50898) + BI4K5 (x(K) 0.55556) |
| BiK-15Gie.tdb | 553 | BIK3_D021 (x(K) 0.75) + BIK3_D03 (x(K) 0.75) + LIQUID (x(K) 0.99987) |
| BiK-15Gie.tdb | 553 | BI2K3 (x(K) 0.6) + BIK3_D021 (x(K) 0.75) + BIK3_D03 (x(K) 0.75) |
| BiK-15Gie.tdb | 541.19 | RHOMBOHEDRAL_A7 (x(K) 0) + LIQUID (x(K) 0.02841) + BI2K_C15 (x(K) 0.33333) |
| BiK-15Gie.tdb | 336.53 | BIK3_D021 (x(K) 0.75) + BCC_A2 (x(K) 1) + LIQUID (x(K) 1) |
| BiK-80Che-LB.tdb | 713.08 | LIQUID (x(K) 0.5896) + BI2K3 (x(K) 0.6) + BIK3_D03 (x(K) 0.75) |
| BiK-80Che-LB.tdb | 713.08 | LIQUID (x(K) 0.58949) + BI2K3 (x(K) 0.6) + BIK3_D03 (x(K) 0.75) |
| BiK-80Che-LB.tdb | 713.08 | LIQUID (x(K) 0.58938) + BI2K3 (x(K) 0.6) + BIK3_D03 (x(K) 0.75) |
| BiK-80Che-LB.tdb | 652.26 | LIQUID (x(K) 0.52504) + BI4K5 (x(K) 0.55556) + BI2K3 (x(K) 0.6) |
| BiK-80Che-LB.tdb | 652.26 | LIQUID (x(K) 0.52514) + BI4K5 (x(K) 0.55556) + BI2K3 (x(K) 0.6) |
| BiK-80Che-LB.tdb | 652.26 | LIQUID (x(K) 0.5249) + BI4K5 (x(K) 0.55556) + BI2K3 (x(K) 0.6) |
| BiK-80Che-LB.tdb | 624.95 | BI2K_C15 (x(K) 0.33333) + LIQUID (x(K) 0.49535) + BI4K5 (x(K) 0.55556) |
| BiK-80Che-LB.tdb | 624.95 | BI2K_C15 (x(K) 0.33333) + LIQUID (x(K) 0.49541) + BI4K5 (x(K) 0.55556) |
| BiK-80Che-LB.tdb | 624.95 | BI2K_C15 (x(K) 0.33333) + LIQUID (x(K) 0.49515) + BI4K5 (x(K) 0.55556) |
| BiK-80Che-LB.tdb | 555.33 | BI2K3 (x(K) 0.6) + BIK3_D021 (x(K) 0.75) + BIK3_D03 (x(K) 0.75) |
| BiK-80Che-LB.tdb | 555.33 | BIK3_D021 (x(K) 0.75) + BIK3_D03 (x(K) 0.75) + LIQUID (x(K) 0.9447) |
| BiK-80Che-LB.tdb | 538.2 | RHOMBOHEDRAL_A7 (x(K) 0) + LIQUID (x(K) 0.02582) + BI2K_C15 (x(K) 0.33333) |
| BiK-80Che-LB.tdb | 538.2 | RHOMBOHEDRAL_A7 (x(K) 0) + LIQUID (x(K) 0.02569) + BI2K_C15 (x(K) 0.33333) |
| BiK-80Che-LB.tdb | 336.32 | BIK3_D021 (x(K) 0.75) + LIQUID (x(K) 0.99949) + BCC_A2 (x(K) 1) |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/BI/BI-K.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/BI/BI-K.json) · [CALPHAD hull BiK-12Niu](https://data.orchid-project.org/hulls/calphad-sgte/BI/BI-K--BiK-12Niu.json) · [CALPHAD hull BiK-80Che-LB](https://data.orchid-project.org/hulls/calphad-sgte/BI/BI-K--BiK-80Che-LB.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Bi–K system (32)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 988 | congruent melting: L -> β-BiK3 | L: K 0.75; β-BiK3: K 0.75 | model | [1] Niu 2012 | Table 2, p. 2, row 29; `ORC-D6GNDMUNID` |  |
| 988 | congruent melting: L -> β-BiK3 | L: K 0.75; β-BiK3: K 0.75 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 28; `ORC-SR52NNJIBP` |  |
| 944 | congruent melting: L -> β-BiK3 | L: K 0.75; β-BiK3: K 0.75 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 27; `ORC-LZA7C54EX2` |  |
| 838 | congruent melting: L -> Bi2K | L: K 0.333; Bi2K: K 0.333 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 21; `ORC-5UBZ5TKNLL` |  |
| 838 | congruent melting: L -> Bi2K | L: K 0.333; Bi2K: K 0.333 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 23; `ORC-EUJ3YH2RMX` |  |
| 838 | congruent melting: L -> Bi2K | L: K 0.333; Bi2K: K 0.333 | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 2, p. 2, row 22; `ORC-UJ6QG7MB4I` |  |
| 838 | congruent melting: L -> Bi2K | L: K 0.333; Bi2K: K 0.333 | model | [1] Niu 2012 | Table 2, p. 2, row 24; `ORC-W4VDWAV7Y7` |  |
| 718 | congruent melting: L -> Bi2K3 | L: K 0.6; Bi2K3: K 0.6 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 25; `ORC-YKREEG4PFG` |  |
| 715.1 | eutectic: L -> Bi2K3 + β-BiK3 | L: K 0.602; Bi2K3: K 0.6; β-BiK3: K 0.75 | model | [1] Niu 2012 | Table 2, p. 2, row 4; `ORC-CMDO4ASO2I` |  |
| 715.1 | congruent melting: L -> Bi2K3 | L: K 0.6; Bi2K3: K 0.6 | model | [1] Niu 2012 | Table 2, p. 2, row 26; `ORC-QHGMPRJTXH` |  |
| 715 | eutectic: L -> Bi2K3 + β-BiK3 | Bi2K3: K 0.6; β-BiK3: K 0.75 | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 2, p. 2, row 2; `ORC-BASZIIGL65` |  |
| 715 | eutectic: L -> Bi2K3 + β-BiK3 | L: K 0.605; Bi2K3: K 0.6; β-BiK3: K 0.75 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 3; `ORC-BUH2BSHAL6` |  |
| 715 | eutectic: L -> Bi2K3 + β-BiK3 | Bi2K3: K 0.6; β-BiK3: K 0.75 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 1; `ORC-E3GIEC6Z7N` |  |
| 654.1 | peritectic: L + Bi2K3 -> Bi4K5 | L: K 0.525; Bi2K3: K 0.6; Bi4K5: K 0.556 | model | [1] Niu 2012 | Table 2, p. 2, row 8; `ORC-OHWCXIRYMQ` |  |
| 654 | peritectic: L + Bi2K3 -> Bi4K5 | Bi2K3: K 0.6; Bi4K5: K 0.556 | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 2, p. 2, row 6; `ORC-3LKXKIQDCG` |  |
| 654 | peritectic: L + Bi2K3 -> Bi4K5 | Bi2K3: K 0.6; Bi4K5: K 0.556 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 5; `ORC-FS5RPBGPIU` |  |
| 654 | peritectic: L + Bi2K3 -> Bi4K5 | L: K 0.535; Bi2K3: K 0.6; Bi4K5: K 0.556 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 7; `ORC-YMHDWREFPZ` |  |
| 628 | eutectic: L -> Bi2K + Bi4K5 | L: K 0.5; Bi2K: K 0.333; Bi4K5: K 0.556 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 11; `ORC-YI5VNOKWUK` |  |
| 627 | eutectic: L -> Bi2K + Bi4K5 | Bi2K: K 0.333; Bi4K5: K 0.556 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 9; `ORC-6UHCXMANFV` |  |
| 627 | eutectic: L -> Bi2K + Bi4K5 | Bi2K: K 0.333; Bi4K5: K 0.556 | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 2, p. 2, row 10; `ORC-I6O6XHVUTI` |  |
| 626.9 | eutectic: L -> Bi2K + Bi4K5 | L: K 0.499; Bi2K: K 0.333; Bi4K5: K 0.556 | model | [1] Niu 2012 | Table 2, p. 2, row 12; `ORC-K67EWIC3ZV` |  |
| 553 | polymorphic: β-BiK3 -> α-BiK3 | β-BiK3: K 0.75; α-BiK3: K 0.75 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 31; `ORC-3PA7LNMM6Z` |  |
| 553 | polymorphic: β-BiK3 -> α-BiK3 | β-BiK3: K 0.75; α-BiK3: K 0.75 | model | [1] Niu 2012 | Table 2, p. 2, row 32; `ORC-3YVCBGP2AO` |  |
| 553 | polymorphic: β-BiK3 -> α-BiK3 | β-BiK3: K 0.75; α-BiK3: K 0.75 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 30; `ORC-PUYZIIHOVC` |  |
| 538.4 | eutectic: L -> Rhom + Bi2K | L: K 0.026; Rhom: K 0; Bi2K: K 0.333 | model | [1] Niu 2012 | Table 2, p. 2, row 16; `ORC-G6PQFWN7IQ` |  |
| 538 | eutectic: L -> Rhom + Bi2K | Bi2K: K 0.333 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 13; `ORC-32DLCM577T` |  |
| 538 | eutectic: L -> Rhom + Bi2K | L: K 0.025; Rhom: K 0; Bi2K: K 0.333 | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 2, p. 2, row 14; `ORC-KKSSSSTWUN` |  |
| 538 | eutectic: L -> Rhom + Bi2K | L: K 0.025; Rhom: K 0; Bi2K: K 0.333 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 15; `ORC-XZ634ZJ3WL` |  |
| 336.71 | eutectic: L -> α-BiK3 + BCC_A2 | L: K 1; α-BiK3: K 0.75; BCC_A2: K 1 | model | [1] Niu 2012; _cites Petric 1991_ [doi](https://doi.org/10.1007/bf02663669) | Table 2, p. 2, row 19; `ORC-RMWZQZYKZM` |  |
| 336.5 | eutectic: L -> α-BiK3 + BCC_A2 | L: K 1; α-BiK3: K 0.75; BCC_A2: K 1 | model | [1] Niu 2012 | Table 2, p. 2, row 20; `ORC-CALF2MSB2U` |  |
| 336 | eutectic: L -> α-BiK3 + BCC_A2 | α-BiK3: K 0.75 | experimental | [1] Niu 2012; _cites Gnutzmann 1961_ [doi](https://doi.org/10.1002/zaac.19613090305) | Table 2, p. 2, row 17; `ORC-CHOUU37D6Y` |  |
| 336 | eutectic: L -> α-BiK3 + BCC_A2 | α-BiK3: K 0.75 | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 2, p. 2, row 18; `ORC-D4SYDI3LFI` |  |

## 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](https://data.orchid-project.org/literature/dft_parity.json).

Table: Enthalpies of formation, Bi–K system (16)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Bi2K | [Bi2K](https://data.orchid-project.org/compounds/Bi2K.html) | -42.5 kJ/mol-atom | 838 | model | -32.149 (mp-aaaabilj) | -30.659 (oqmd-647551) | [1] Niu 2012 | Table 3, p. 4, row 6; `ORC-AENQCHXMTS.f8b618` |  |
| Bi2K | [Bi2K](https://data.orchid-project.org/compounds/Bi2K.html) | -41 kJ/mol-atom ± 4.2 | 838 | unspecified | -32.149 (mp-aaaabilj) | -30.659 (oqmd-647551) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 4; `ORC-4ABBGGQFFI.4ac59d` |  |
| Bi2K | [Bi2K](https://data.orchid-project.org/compounds/Bi2K.html) | -40.8 kJ/mol-atom | 838 | experimental | -32.149 (mp-aaaabilj) | -30.659 (oqmd-647551) | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 3, p. 4, row 5; `ORC-KEI2TY2L4J.d9b859` |  |
| Bi2K | [Bi2K](https://data.orchid-project.org/compounds/Bi2K.html) | -34.2 kJ/mol-atom | 523 | model | -32.149 (mp-aaaabilj) | -30.659 (oqmd-647551) | [1] Niu 2012 | Table 3, p. 4, row 3; `ORC-L3UASAPG7V.77de70` |  |
| Bi2K | [Bi2K](https://data.orchid-project.org/compounds/Bi2K.html) | -28.7 kJ/mol-atom ± 2.2 | 523 | experimental | -32.149 (mp-aaaabilj) | -30.659 (oqmd-647551) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 1; `ORC-OAM7DL5O44.d94368` |  |
| Bi2K3 | [Bi2K3](https://data.orchid-project.org/compounds/Bi2K3.html) | -43.2 kJ/mol-atom | 523 | model | -31.875 (mp-aaacqqwr) | -33.986 (oqmd-1435539) | [1] Niu 2012 | Table 3, p. 4, row 14; `ORC-HMQVDKAC42.7fa48f` |  |
| Bi2K3 | [Bi2K3](https://data.orchid-project.org/compounds/Bi2K3.html) | -39.5 kJ/mol-atom ± 2.2 | 523 | experimental | -31.875 (mp-aaacqqwr) | -33.986 (oqmd-1435539) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 12; `ORC-5VLZZSK2FU.d897be` |  |
| Bi4K5 | [Bi4K5](https://data.orchid-project.org/compounds/Bi4K5.html) | -50.2 kJ/mol-atom ± 12.6 | 627 | unspecified | -33.867 (mp-aaacrqif) | -36.015 (oqmd-1339793) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 10; `ORC-3L3YEMNECR.64f811` |  |
| Bi4K5 | [Bi4K5](https://data.orchid-project.org/compounds/Bi4K5.html) | -48.4 kJ/mol-atom | 627 | model | -33.867 (mp-aaacrqif) | -36.015 (oqmd-1339793) | [1] Niu 2012 | Table 3, p. 4, row 11; `ORC-GCE5VEZUQX.c71912` |  |
| Bi4K5 | [Bi4K5](https://data.orchid-project.org/compounds/Bi4K5.html) | -42.1 kJ/mol-atom | 523 | model | -33.867 (mp-aaacrqif) | -36.015 (oqmd-1339793) | [1] Niu 2012 | Table 3, p. 4, row 9; `ORC-YXG4J56R7H.cd78ca` |  |
| Bi4K5 | [Bi4K5](https://data.orchid-project.org/compounds/Bi4K5.html) | -38.1 kJ/mol-atom ± 2.2 | 523 | experimental | -33.867 (mp-aaacrqif) | -36.015 (oqmd-1339793) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 7; `ORC-JHECAZUR7A.c83958` |  |
| BiK3 | [BiK3](https://data.orchid-project.org/compounds/BiK3.html) | -51.3 kJ/mol-atom | 848 | model | -35.228 (mp-aaaabuhi) | -37.486 (oqmd-24983) | [1] Niu 2012 | Table 3, p. 4, row 19; `ORC-ABC2SN45RE.77a958` |  |
| BiK3 | [BiK3](https://data.orchid-project.org/compounds/BiK3.html) | -49.2 kJ/mol-atom | 848 | experimental | -35.228 (mp-aaaabuhi) | -37.486 (oqmd-24983) | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 3, p. 4, row 18; `ORC-K4G26RVS4P.72381c` |  |
| BiK3 | [BiK3](https://data.orchid-project.org/compounds/BiK3.html) | -46.7 kJ/mol-atom | 523 | model | -35.228 (mp-aaaabuhi) | -37.486 (oqmd-24983) | [1] Niu 2012 | Table 3, p. 4, row 17; `ORC-JX6VRWVKQ6.417946` |  |
| BiK3 | [BiK3](https://data.orchid-project.org/compounds/BiK3.html) | -45.1 kJ/mol-atom ± 2.1 | 523 | experimental | -35.228 (mp-aaaabuhi) | -37.486 (oqmd-24983) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 15; `ORC-AP6PJYWU2A.68996d` |  |
| BiK3 | [BiK3](https://data.orchid-project.org/compounds/BiK3.html) | 45.1 kJ/mol-atom ± 2.1 | 523 | experimental | -35.228 (mp-aaaabuhi) | -37.486 (oqmd-24983) | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 15; `ORC-AP6PJYWU2A.b4b400` |  |

## Other properties

### Phase transition (1)

Table: Phase transition, Bi–K system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 553.15 K | 553.15 | polymorphic | experimental | [1] Niu 2012; _cites Smith 1908_ | p. 1; `ORC-F7ZQXODI33` | “Both Smith \[7\] and Gnutzmann and Klemm \[8\] found that the BiK3 compound undergoes a polymorphic transformation at 280 ± 5 ◦ C.” |

### Formation (34)

Table: Formation, Bi–K system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy of formation; _printed: ΔfS_ | -2.9 J/mol-atom/K | 523 | Bi2K; _alloy: K 0.333333_ | model | [1] Niu 2012 | Table 3, p. 4, row 3; `ORC-L3UASAPG7V.5ab8f3` |  |
| Entropy of formation; _printed: ΔfS_ | -3.4 J/mol-atom/K ± 6.3 | 523 | Bi2K; _alloy: K 0.333333_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 1; `ORC-OAM7DL5O44.ba4057` |  |
| Entropy of formation; _printed: ΔfS_ | -8.4 J/mol-atom/K ± 4.6 | 523 | Bi2K3; _alloy: K 0.6_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 12; `ORC-5VLZZSK2FU.d33407` |  |
| Entropy of formation; _printed: ΔfS_ | -6.52 J/mol-atom/K | 523 | Bi2K3; _alloy: K 0.6_ | model | [1] Niu 2012 | Table 3, p. 4, row 14; `ORC-HMQVDKAC42.fb09f1` |  |
| Entropy of formation; _printed: ΔfS_ | -8.4 J/mol-atom/K ± 5 | 523 | Bi4K5; _alloy: K 0.555556_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 7; `ORC-JHECAZUR7A.b9ac78` |  |
| Entropy of formation; _printed: ΔfS_ | -6.1 J/mol-atom/K | 523 | Bi4K5; _alloy: K 0.555556_ | model | [1] Niu 2012 | Table 3, p. 4, row 9; `ORC-YXG4J56R7H.c49697` |  |
| Entropy of formation; _printed: ΔfS_ | -19.7 J/mol-atom/K ± 3.8 | 523 | BiK3; _alloy: K 0.75_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 15; `ORC-AP6PJYWU2A.7b2fd9` |  |
| Entropy of formation; _printed: ΔfS_ | -12 J/mol-atom/K | 523 | BiK3; _alloy: K 0.75_ | model | [1] Niu 2012 | Table 3, p. 4, row 17; `ORC-JX6VRWVKQ6.189ebf` |  |
| Entropy of formation; _printed: ΔfS_ | -23.4 J/mol-atom/K ± 6.3 | 627 | Bi4K5; _alloy: K 0.555556_ | unspecified | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 10; `ORC-3L3YEMNECR.043849` |  |
| Entropy of formation; _printed: ΔfS_ | -19.2 J/mol-atom/K | 627 | Bi4K5; _alloy: K 0.555556_ | model | [1] Niu 2012 | Table 3, p. 4, row 11; `ORC-GCE5VEZUQX.0722d2` |  |
| Entropy of formation; _printed: ΔfS_ | -17.2 J/mol-atom/K ± 4.2 | 838 | Bi2K; _alloy: K 0.333333_ | unspecified | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 4; `ORC-4ABBGGQFFI.0e7eb4` |  |
| Entropy of formation; _printed: ΔfS_ | -19 J/mol-atom/K | 838 | Bi2K; _alloy: K 0.333333_ | model | [1] Niu 2012 | Table 3, p. 4, row 6; `ORC-AENQCHXMTS.bec032` |  |
| Entropy of formation; _printed: ΔfS_ | -16.9 J/mol-atom/K | 838 | Bi2K; _alloy: K 0.333333_ | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 3, p. 4, row 5; `ORC-KEI2TY2L4J.b8e593` |  |
| Entropy of formation; _printed: ΔfS_ | -22.4 J/mol-atom/K | 848 | BiK3; _alloy: K 0.75_ | model | [1] Niu 2012 | Table 3, p. 4, row 19; `ORC-ABC2SN45RE.bd5f5f` |  |
| Entropy of formation; _printed: ΔfS_ | -19.9 J/mol-atom/K | 848 | BiK3; _alloy: K 0.75_ | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 3, p. 4, row 18; `ORC-K4G26RVS4P.ff46e0` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -32.7 kJ/mol-atom | 523 | Bi2K; _alloy: K 0.333333_ | model | [1] Niu 2012 | Table 3, p. 4, row 3; `ORC-L3UASAPG7V.fd357e` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -26.5 kJ/mol-atom ± 1.3 | 523 | Bi2K; _alloy: K 0.333333_ | experimental | [1] Niu 2012; _cites Hultgren 1973_ | Table 3, p. 4, row 2; `ORC-MVMC4LLIGK.4b419f` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -27 kJ/mol-atom ± 5.5 | 523 | Bi2K; _alloy: K 0.333333_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 1; `ORC-OAM7DL5O44.eae81e` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -34 kJ/mol-atom ± 1.3 | 523 | Bi2K3; _alloy: K 0.6_ | experimental | [1] Niu 2012; _cites Hultgren 1973_ | Table 3, p. 4, row 13; `ORC-5MBL67NU55.878bc8` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -35.2 kJ/mol-atom ± 4.6 | 523 | Bi2K3; _alloy: K 0.6_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 12; `ORC-5VLZZSK2FU.913e31` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -39.8 kJ/mol-atom | 523 | Bi2K3; _alloy: K 0.6_ | model | [1] Niu 2012 | Table 3, p. 4, row 14; `ORC-HMQVDKAC42.422641` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -33.1 kJ/mol-atom ± 1.3 | 523 | Bi4K5; _alloy: K 0.555556_ | experimental | [1] Niu 2012; _cites Hultgren 1973_ | Table 3, p. 4, row 8; `ORC-GPYTLM7TMH.7ab976` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -33.7 kJ/mol-atom ± 4.8 | 523 | Bi4K5; _alloy: K 0.555556_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 7; `ORC-JHECAZUR7A.791202` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -38.9 kJ/mol-atom | 523 | Bi4K5; _alloy: K 0.555556_ | model | [1] Niu 2012 | Table 3, p. 4, row 9; `ORC-YXG4J56R7H.21672e` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -33.9 kJ/mol-atom ± 1.3 | 523 | BiK3; _alloy: K 0.75_ | experimental | [1] Niu 2012; _cites Hultgren 1973_ | Table 3, p. 4, row 16; `ORC-65FTHM43WD.50bd46` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -34.8 kJ/mol-atom ± 4.1 | 523 | BiK3; _alloy: K 0.75_ | experimental | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 15; `ORC-AP6PJYWU2A.b9ea98` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -40.4 kJ/mol-atom | 523 | BiK3; _alloy: K 0.75_ | model | [1] Niu 2012 | Table 3, p. 4, row 17; `ORC-JX6VRWVKQ6.9d3809` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -35.5 kJ/mol-atom ± 16.5 | 627 | Bi4K5; _alloy: K 0.555556_ | unspecified | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 10; `ORC-3L3YEMNECR.e584f7` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -36.4 kJ/mol-atom | 627 | Bi4K5; _alloy: K 0.555556_ | model | [1] Niu 2012 | Table 3, p. 4, row 11; `ORC-GCE5VEZUQX.f53510` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -26.6 kJ/mol-atom ± 7.7 | 838 | Bi2K; _alloy: K 0.333333_ | unspecified | [1] Niu 2012; _cites Voronin 1971_ | Table 3, p. 4, row 4; `ORC-4ABBGGQFFI.4742eb` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -26.6 kJ/mol-atom | 838 | Bi2K; _alloy: K 0.333333_ | model | [1] Niu 2012 | Table 3, p. 4, row 6; `ORC-AENQCHXMTS.8aebf2` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -26.6 kJ/mol-atom | 838 | Bi2K; _alloy: K 0.333333_ | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 3, p. 4, row 5; `ORC-KEI2TY2L4J.c69d64` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -32.3 kJ/mol-atom | 848 | BiK3; _alloy: K 0.75_ | model | [1] Niu 2012 | Table 3, p. 4, row 19; `ORC-ABC2SN45RE.6bdb79` |  |
| Gibbs energy of formation; _printed: ΔfG_ | -32.4 kJ/mol-atom | 848 | BiK3; _alloy: K 0.75_ | experimental | [1] Niu 2012; _cites Petric 1988_ [doi](https://doi.org/10.1088/0305-4608/18/7/015) | Table 3, p. 4, row 18; `ORC-K4G26RVS4P.4000e4` |  |

## Sources

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

1. Chunju Niu, Changrong Li, Zhenmin Du, Cuiping Guo, Miao Liu, Thermodynamic assessment of the Bi–K binary system, Thermochimica Acta 528, 9-14 (2012). [doi:10.1016/j.tca.2011.10.032](https://doi.org/10.1016/j.tca.2011.10.032)

## 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). https://doi.org/10.5281/zenodo.23735569
- R. Arróyave, J. Saal, D. Shin, ORCHID-Diagrams: calculated binary phase diagrams (version 2026.10), Zenodo (2026). https://doi.org/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). https://doi.org/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). https://doi.org/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.

```bibtex
@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}
}
```

---

Derived data CC BY 4.0 ([licence](https://creativecommons.org/licenses/by/4.0/)): cite ORCHID ([CITATION.cff](https://data.orchid-project.org/CITATION.cff)) and the original sources. Quotes are short excerpts kept so that each value can be checked; they remain under the publishers' copyright and are not relicensed. Source papers, page images and full text are not redistributed. Field reference: [SCHEMA.md](https://data.orchid-project.org/literature/SCHEMA.md). Machine-readable guide: [llms.txt](https://data.orchid-project.org/llms.txt). Found an error? The report link of a value (Markdown: its id, ORC-..., in the Location column) opens a pre-filled GitHub issue, https://github.com/orchid-calphad/orchid-data/issues/new?template=report-value-error.yml&record_id=\<id>, carrying only the record id, source and value; [how to contribute](https://orchid-project.org/contribute/).