# Hf–Si system

> Hf–Si system: 62 accepted literature values (invariant reaction 38, crystal structure 14, formation 7, phase transition 2) and 3 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

HTML: https://data.orchid-project.org/systems/HF-SI.html · Markdown: https://data.orchid-project.org/systems/HF-SI.md

62 accepted literature values from 2 paper(s) (experimental 24, model 21, unspecified 17); 3 calculated phase diagram(s). 1 further extracted value(s) not accepted by the reader-agreement checks are only in the JSON/CSV.

Data: [JSON](https://data.orchid-project.org/literature/systems/HF-SI.json) · [CSV](https://data.orchid-project.org/systems/HF-SI.csv) · [interactive explorer](https://orchid-project.org/data-explorer/#HF-SI) · [interactive phase diagram](https://orchid-project.org/phase-diagrams/#HF-SI/HfSi-00Zha-LB.json) · [phases (11)](https://data.orchid-project.org/phases/pages/HF-SI.html) · [papers (bibliography)](https://data.orchid-project.org/bibliography/pages/systems/HF-SI.html) · [Markdown](https://data.orchid-project.org/systems/HF-SI.md)

Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 24 |
| model | 21 |
| unspecified | 17 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 38 |
| phase transition | 2 |
| phase equilibrium | 1 |
| formation | 7 |
| crystal structure | 14 |

## 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 |
|---|---|---|---|
| HfSi-00Zha-LB.tdb | J.-C. Zhao, B.P. Bewlay, M.R. Jackson, Q. Chen, J. Phase Equilib., 21, 40-45(2000). [doi:10.1361/105497100770340408](https://doi.org/10.1361/105497100770340408) | `29edae6cd520ee5ecd21bc7319503170e0c06e87814f7ec0b538a116cdc2974a` | [viewer](https://orchid-project.org/phase-diagrams/#HF-SI/HfSi-00Zha-LB.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/HfSi-00Zha-LB.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/HfSi-00Zha-LB.json) |
| HfSi-03Yan.tdb | Y. Yang, Y.A. Chang, J.-C. Zhao, B.P. Bewlay, Intermetallics, 11, 407-15(2003). [doi:10.1016/S0966-9795(03)00021-9](https://doi.org/10.1016/S0966-9795%2803%2900021-9) | `4c947308a5e5f90e20ce2fef31966e5c327be89ea8f9139bbcac842ece1718a5` | [viewer](https://orchid-project.org/phase-diagrams/#HF-SI/HfSi-03Yan.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/HfSi-03Yan.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/HfSi-03Yan.json) |
| HfSi-19Hon.tdb | P. Honarmandi, T.C. Duong, S.F. Ghoreishi, D. Allaire, R. Arroyave, Acta Mater., 164, 636-47(2019). [doi:10.1016/j.actamat.2018.11.007](https://doi.org/10.1016/j.actamat.2018.11.007) | `6640e20000baa136ef728ec703943e8f48e3ac577f918febf3c256616195ab32` | [viewer](https://orchid-project.org/phase-diagrams/#HF-SI/HfSi-19Hon.json) · [TDB](https://orchid-project.org/data/databases/sgte-binary/HfSi-19Hon.tdb) · [JSON](https://data.orchid-project.org/phase-diagrams/sgte/HfSi-19Hon.json) |

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

| TDB file | T (K) | Phases at the invariant |
|---|---:|---|
| HfSi-00Zha-LB.tdb | 2630 | LIQUID (x(Si) 0.27716) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-00Zha-LB.tdb | 2630 | LIQUID (x(Si) 0.27723) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-00Zha-LB.tdb | 2630 | LIQUID (x(Si) 0.2773) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-00Zha-LB.tdb | 2586.56 | HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) + LIQUID (x(Si) 0.546) |
| HfSi-00Zha-LB.tdb | 2586.56 | HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) + LIQUID (x(Si) 0.54591) |
| HfSi-00Zha-LB.tdb | 2405.82 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.62827) |
| HfSi-00Zha-LB.tdb | 2405.82 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.62813) |
| HfSi-00Zha-LB.tdb | 2405.82 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.62832) |
| HfSi-00Zha-LB.tdb | 2358.67 | LIQUID (x(Si) 0.17886) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-00Zha-LB.tdb | 2358.67 | LIQUID (x(Si) 0.17878) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-00Zha-LB.tdb | 2358.67 | LIQUID (x(Si) 0.17874) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-00Zha-LB.tdb | 2197.56 | HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-00Zha-LB.tdb | 2101.49 | BCC_A2 (x(Si) 3.000e-5) + LIQUID (x(Si) 0.11111) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-00Zha-LB.tdb | 2101.49 | BCC_A2 (x(Si) 3.000e-5) + LIQUID (x(Si) 0.1111) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-00Zha-LB.tdb | 2016 | HCP_A3 (x(Si) 1.000e-5) + BCC_A2 (x(Si) 2.000e-5) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-00Zha-LB.tdb | 1818.85 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.80817) |
| HfSi-00Zha-LB.tdb | 1818.85 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.80808) |
| HfSi-00Zha-LB.tdb | 1818.85 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.80823) |
| HfSi-00Zha-LB.tdb | 1597.92 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.90793) + DIAMOND_A4 (x(Si) 1) |
| HfSi-00Zha-LB.tdb | 1597.92 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.90806) + DIAMOND_A4 (x(Si) 1) |
| HfSi-00Zha-LB.tdb | 1597.92 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.9081) + DIAMOND_A4 (x(Si) 1) |
| HfSi-03Yan.tdb | 2626.92 | LIQUID (x(Si) 0.30282) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-03Yan.tdb | 2626.92 | LIQUID (x(Si) 0.30294) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-03Yan.tdb | 2626.92 | LIQUID (x(Si) 0.303) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-03Yan.tdb | 2595.12 | HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) + LIQUID (x(Si) 0.50837) |
| HfSi-03Yan.tdb | 2595.12 | HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) + LIQUID (x(Si) 0.50822) |
| HfSi-03Yan.tdb | 2416.93 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.58357) |
| HfSi-03Yan.tdb | 2416.93 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.58352) |
| HfSi-03Yan.tdb | 2416.93 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.58364) |
| HfSi-03Yan.tdb | 2365.31 | LIQUID (x(Si) 0.20984) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-03Yan.tdb | 2365.31 | LIQUID (x(Si) 0.20971) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-03Yan.tdb | 2365.31 | LIQUID (x(Si) 0.20968) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-03Yan.tdb | 2199.07 | HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-03Yan.tdb | 2099.95 | BCC_A2 (x(Si) 1.000e-5) + LIQUID (x(Si) 0.12438) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-03Yan.tdb | 2099.95 | BCC_A2 (x(Si) 1.000e-5) + LIQUID (x(Si) 0.12433) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-03Yan.tdb | 2016.02 | HCP_A3 (x(Si) 0) + BCC_A2 (x(Si) 1.000e-5) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-03Yan.tdb | 1814.55 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.76149) |
| HfSi-03Yan.tdb | 1814.55 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.76139) |
| HfSi-03Yan.tdb | 1814.55 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.76151) |
| HfSi-03Yan.tdb | 1602.75 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.89283) + DIAMOND_A4 (x(Si) 1) |
| HfSi-03Yan.tdb | 1602.75 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.89285) + DIAMOND_A4 (x(Si) 1) |
| HfSi-03Yan.tdb | 1602.75 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.8929) + DIAMOND_A4 (x(Si) 1) |
| HfSi-19Hon.tdb | 2740.16 | LIQUID (x(Si) 0.3616) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-19Hon.tdb | 2740.16 | LIQUID (x(Si) 0.36052) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-19Hon.tdb | 2740.15 | LIQUID (x(Si) 0.36104) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-19Hon.tdb | 2577.43 | HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) + LIQUID (x(Si) 0.54873) |
| HfSi-19Hon.tdb | 2577.43 | HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) + LIQUID (x(Si) 0.54894) |
| HfSi-19Hon.tdb | 2402.04 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.62957) |
| HfSi-19Hon.tdb | 2402.04 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.62956) |
| HfSi-19Hon.tdb | 2402.04 | HF5SI4 (x(Si) 0.44444) + HFSI_B27 (x(Si) 0.5) + LIQUID (x(Si) 0.62969) |
| HfSi-19Hon.tdb | 2224.3 | LIQUID (x(Si) 0.1447) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-19Hon.tdb | 2224.3 | LIQUID (x(Si) 0.14462) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-19Hon.tdb | 2224.3 | LIQUID (x(Si) 0.14462) + HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) |
| HfSi-19Hon.tdb | 2151.35 | BCC_A2 (x(Si) 0.00211) + LIQUID (x(Si) 0.12537) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-19Hon.tdb | 2151.35 | BCC_A2 (x(Si) 0.00211) + LIQUID (x(Si) 0.12537) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-19Hon.tdb | 2013.35 | HCP_A3 (x(Si) 6.700e-4) + BCC_A2 (x(Si) 0.00113) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-19Hon.tdb | 2013.35 | HCP_A3 (x(Si) 6.600e-4) + BCC_A2 (x(Si) 0.00113) + HF2SI_C16 (x(Si) 0.33333) |
| HfSi-19Hon.tdb | 1816.93 | HF2SI_C16 (x(Si) 0.33333) + HF5SI3_D88 (x(Si) 0.375) + HF3SI2_D5A (x(Si) 0.4) |
| HfSi-19Hon.tdb | 1807.63 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.80902) |
| HfSi-19Hon.tdb | 1807.63 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.80888) |
| HfSi-19Hon.tdb | 1807.63 | HFSI_B27 (x(Si) 0.5) + HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.80903) |
| HfSi-19Hon.tdb | 1609.18 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.90012) + DIAMOND_A4 (x(Si) 1) |
| HfSi-19Hon.tdb | 1609.18 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.90034) + DIAMOND_A4 (x(Si) 1) |
| HfSi-19Hon.tdb | 1609.18 | HFSI2_C49 (x(Si) 0.66667) + LIQUID (x(Si) 0.90041) + DIAMOND_A4 (x(Si) 1) |
| HfSi-19Hon.tdb | 383.39 | HF2SI_C16 (x(Si) 0.33333) + HF3SI2_D5A (x(Si) 0.4) + HF5SI4 (x(Si) 0.44444) |

Convex hulls: [Materials Project DFT hull](https://data.orchid-project.org/hulls/dft-mp/HF/HF-SI.json) · [OQMD DFT hull](https://data.orchid-project.org/hulls/dft-oqmd/HF/HF-SI.json) · [CALPHAD hull HfSi-00Zha-LB](https://data.orchid-project.org/hulls/calphad-sgte/HF/HF-SI--HfSi-00Zha-LB.json) · [CALPHAD hull HfSi-03Yan](https://data.orchid-project.org/hulls/calphad-sgte/HF/HF-SI--HfSi-03Yan.json)

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Hf–Si system (38)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 2753.15 | congruent melting: L->Hf3Si2 | L: Si 0.4; Hf3Si2: Hf 0.6, Si 0.4 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 21; `ORC-DQXMHMYEPN` |  |
| 2736.15 | congruent melting: L->Hf3Si2 | L: Si 0.4; Hf3Si2: Hf 0.6, Si 0.4 | model | [1] Yang 2003 | Table 3, p. 3, row 20; `ORC-NM74MT6ONK` |  |
| 2633.15 | L+Hf3Si2->Hf5Si3 | Hf3Si2: Hf 0.6, Si 0.4; Hf5Si3: Hf 0.625, Si 0.375 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 7; `ORC-2CQHYEOYAE` |  |
| 2633.15 | peritectic: L + Hf3Si2 -> Hf5Si3 | Hf3Si2: Si 0.4; Hf5Si3: Si 0.375 | model | [2] Zhao 2000 | Table 2, p. 2, row 7; `ORC-VHBKKZEWW6` |  |
| 2630.15 | peritectic: L + Hf3Si2 -> Hf5Si3 | L: Si 0.277; Hf3Si2: Si 0.4; Hf5Si3: Si 0.375 | model | [2] Zhao 2000 | Table 2, p. 2, row 8; `ORC-AVOEOJDPZI` |  |
| 2628.15 | L+Hf3Si2->Hf5Si3 | L: Si 0.303; Hf3Si2: Si 0.4; Hf5Si3: Si 0.375 | model | [1] Yang 2003 | Table 3, p. 3, row 6; `ORC-WULEIWIIBV` |  |
| 2594.15 | L+Hf3Si2->Hf5Si4 | L: Si 0.509; Hf3Si2: Si 0.4; Hf5Si4: Si 0.444 | model | [1] Yang 2003 | Table 3, p. 3, row 10; `ORC-RHSO3CYW7P` |  |
| 2593.15 | peritectic: Hf3Si2 + L -> Hf5Si4 | Hf3Si2: Si 0.4; Hf5Si4: Si 0.444444 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 13; `ORC-4UOALP6XD3` |  |
| 2593.15 | L+Hf3Si2->Hf5Si4 | Hf3Si2: Hf 0.6, Si 0.4; Hf5Si4: Hf 0.555556, Si 0.444444 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 11; `ORC-DWDYXR6IPF` |  |
| 2586.15 | peritectic: Hf3Si2 + L -> Hf5Si4 | Hf3Si2: Si 0.4; L: Si 0.546; Hf5Si4: Si 0.444444 | model | [2] Zhao 2000 | Table 2, p. 2, row 14; `ORC-OVXPJMYGV6` |  |
| 2418.15 | L+Hf5Si4->HfSi | L: Si 0.583; Hf5Si4: Si 0.444; HfSi: Si 0.5 | model | [1] Yang 2003 | Table 3, p. 3, row 12; `ORC-MCVK6PUZ53` |  |
| 2415.15 | L+Hf5Si4->HfSi | Hf5Si4: Hf 0.555556, Si 0.444444; HfSi: Hf 0.5, Si 0.5 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 13; `ORC-7MTHVOCIYL` |  |
| 2415.15 | peritectic: Hf5Si4 + L -> HfSi | Hf5Si4: Si 0.444444; HfSi: Si 0.5 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 15; `ORC-H72LOCV5FE` |  |
| 2406.15 | peritectic: Hf5Si4 + L -> HfSi | Hf5Si4: Si 0.444444; L: Si 0.628; HfSi: Si 0.5 | model | [2] Zhao 2000 | Table 2, p. 2, row 16; `ORC-OTHNIGW3GL` |  |
| 2365.15 | L+Hf5Si3->Hf2Si | L: Si 0.21; Hf5Si3: Si 0.375; Hf2Si: Si 0.333 | model | [1] Yang 2003 | Table 3, p. 3, row 3; `ORC-2P6V6S2LGP` |  |
| 2359.15 | L+Hf5Si3->Hf2Si | L: Si 0.179; Hf5Si3: Si 0.375; Hf2Si: Si 0.333 | model | [1] Yang 2003; _cites Zhao 2000_ [doi](https://doi.org/10.1361/105497100770340408) | Table 3, p. 3, row 4; `ORC-5SBTCW5JSK` |  |
| 2359.15 | peritectic: L + Hf5Si3 -> Hf2Si | L: Si 0.179; Hf5Si3: Si 0.375; Hf2Si: Si 0.333333 | model | [2] Zhao 2000 | Table 2, p. 2, row 6; `ORC-HAMW4VEQLF` |  |
| 2356.15 | L+Hf5Si3->Hf2Si | Hf5Si3: Hf 0.625, Si 0.375; Hf2Si: Hf 0.666667, Si 0.333333 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 5; `ORC-CGUG24XROZ` |  |
| 2356.15 | peritectic: L + Hf5Si3 -> Hf2Si | Hf5Si3: Si 0.375; Hf2Si: Si 0.333333 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 5; `ORC-RKDK4PMRKG` |  |
| 2198.15 | eutectoid: Hf5Si3 -> Hf2Si + Hf3Si2 | Hf5Si3: Si 0.375; Hf2Si: Si 0.333333; Hf3Si2: Si 0.4 | experimental | [2] Zhao 2000 | Table 2, p. 2, row 9; `ORC-CC2JCK7FEQ` |  |
| 2198.15 | Hf5Si3->Hf2Si+Hf3Si2 | Hf5Si3: Si 0.375; Hf2Si: Si 0.333; Hf3Si2: Si 0.4 | model | [1] Yang 2003 | Table 3, p. 3, row 8; `ORC-EX5PPSA2LA` |  |
| 2198.15 | Hf5Si3->Hf2Si+Hf3Si2 | Hf5Si3: Hf 0.625, Si 0.375; Hf2Si: Hf 0.666667, Si 0.333333; Hf3Si2: Si 0.4 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 9; `ORC-NOCQ4FOP3B` |  |
| 2198.15 | eutectoid: Hf5Si3 ↔ Hf2Si + Hf3Si2 |  | experimental | [2] Zhao 2000 | p. 3; `ORC-PO4HMQJLBW` | “Based on the above data, it is clear that the eutectoid reaction, Hf5Si3 ↔ Hf2Si + Hf3Si2, exists at 1925 ± 25 °C.” |
| 2197.15 | eutectoid: Hf5Si3 -> Hf2Si + Hf3Si2 | Hf5Si3: Si 0.375; Hf2Si: Si 0.333333; Hf3Si2: Si 0.4 | model | [2] Zhao 2000 | Table 2, p. 2, row 10; `ORC-RQL2F54TO4` |  |
| 2104.15 | eutectic: L->bcc(Hf)+Hf2Si | L: Si 0.115; Hf2Si: Hf 0.666667, Si 0.333333 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 2; `ORC-25R37SRK3W` |  |
| 2104.15 | eutectic: L -> bcc (Hf) + Hf2Si | L: Si 0.115; Hf2Si: Si 0.333333 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 1; `ORC-AKI5TVHLB7` |  |
| 2101.15 | eutectic: L -> bcc (Hf) + Hf2Si | L: Si 0.111; Hf2Si: Si 0.333333 | model | [2] Zhao 2000 | Table 2, p. 2, row 2; `ORC-65PMR7I7UG` |  |
| 2100.15 | eutectic: L->bcc(Hf)+Hf2Si | L: Si 0.12; bcc(Hf): Si 0; Hf2Si: Si 0.333 | model | [1] Yang 2003 | Table 3, p. 3, row 1; `ORC-FJWGWYT7K5` |  |
| 2016.15 | peritectoid: Bcc (Hf) + Hf2Si -> hcp (Hf) | Hf2Si: Si 0.333333 | model | [2] Zhao 2000 | Table 2, p. 2, row 4; `ORC-EXIAXQ3DVI` |  |
| 2016.15 | peritectoid: Bcc (Hf) + Hf2Si -> hcp (Hf) | Hf2Si: Si 0.333333 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 3; `ORC-VNGYTCEOCN` |  |
| 1819.15 | peritectic: HfSi + L -> HfSi2 | HfSi: Si 0.5; L: Si 0.808; HfSi2: Si 0.666667 | model | [2] Zhao 2000 | Table 2, p. 2, row 18; `ORC-TGND66FJPY` |  |
| 1816.15 | peritectic: HfSi + L -> HfSi2 | HfSi: Si 0.5; HfSi2: Si 0.666667 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 17; `ORC-EWSMTAZE3V` |  |
| 1816.15 | L+HfSi->HfSi2 | HfSi: Hf 0.5, Si 0.5; HfSi2: Hf 0.333333, Si 0.666667 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 15; `ORC-VLFUIXB7CY` |  |
| 1814.15 | L+HfSi->HfSi2 | L: Si 0.762; HfSi: Si 0.5; HfSi2: Si 0.667 | model | [1] Yang 2003 | Table 3, p. 3, row 14; `ORC-VK76LKTZIN` |  |
| 1603.15 | eutectic: L->HfSi2+(Si) | L: Si 0.91; HfSi2: Hf 0.333333, Si 0.666667 | experimental | [1] Yang 2003; _cites Brukl 1968_ | Table 3, p. 3, row 17; `ORC-6RBWCTLYHD` |  |
| 1603.15 | eutectic: L -> HfSi2 + diamond_A4 (Si) | L: Si 0.91; HfSi2: Si 0.666667; diamond_A4 (Si): Si 1 | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 19; `ORC-II2T7VPYPT` |  |
| 1603.15 | eutectic: L->HfSi2+(Si) | L: Si 0.893; HfSi2: Si 0.667; (Si): Si 1 | model | [1] Yang 2003 | Table 3, p. 3, row 16; `ORC-SHNFFIRUSD` |  |
| 1598.15 | eutectic: L -> HfSi2 + diamond_A4 (Si) | L: Si 0.908; HfSi2: Si 0.666667; diamond_A4 (Si): Si 1 | model | [2] Zhao 2000 | Table 2, p. 2, row 20; `ORC-G53DU67IYP` |  |

## 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, Hf–Si system (7)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Hf2Si | [Hf2Si](https://data.orchid-project.org/compounds/Hf2Si.html) | -62.7 kJ/mol-atom | 298.15 | unspecified | -69.475 (mp-aaaaaosg) | -71.646 (oqmd-7793) | [2] Zhao 2000; _cites Samsonov 1980_ [doi](https://doi.org/10.1007/978-1-4684-6099-5) | Table 3, p. 3, row 1; `ORC-XMCR6DJ76G` |  |
| Hf3Si2 | [Hf3Si2](https://data.orchid-project.org/compounds/Hf3Si2.html) | -80 kJ/mol-atom ± 4.7 | 1473 | experimental | -74.298 (mp-aaaaadcz) | -77.301 (oqmd-647083) | [2] Zhao 2000; _cites Topor 1990_ [doi](https://doi.org/10.1016/0022-5088%2890%2990292-r) | Table 3, p. 3, row 9; `ORC-GVZJCFBURB.d0f825` |  |
| Hf5Si3 | [Hf5Si3](https://data.orchid-project.org/compounds/Hf5Si3.html) | -70.2 kJ/mol-atom | 298.15 | unspecified | -69.268 (mp-aaaaaxqb) | -71.886 (oqmd-647084) | [2] Zhao 2000; _cites Samsonov 1980_ [doi](https://doi.org/10.1007/978-1-4684-6099-5) | Table 3, p. 3, row 5; `ORC-CH4W63JO64` |  |
| Hf5Si3 | [Hf5Si3](https://data.orchid-project.org/compounds/Hf5Si3.html) | -70.2 kJ/mol-atom ± 3.3 | 298.15 | experimental | -69.268 (mp-aaaaaxqb) | -71.886 (oqmd-647084) | [2] Zhao 2000; _cites Golutvin 1971_ | Table 3, p. 3, row 4; `ORC-NSLZ5NLCAN.5e930d` |  |
| HfSi | [HfSi](https://data.orchid-project.org/compounds/HfSi.html) | -71.1 kJ/mol-atom | 298.15 | unspecified | -75.502 (mp-aaaaaboc) | -79.13 (oqmd-647082) | [2] Zhao 2000; _cites Samsonov 1980_ [doi](https://doi.org/10.1007/978-1-4684-6099-5) | Table 3, p. 3, row 13; `ORC-IEUGQ7CJKP` |  |
| HfSi | [HfSi](https://data.orchid-project.org/compounds/HfSi.html) | -71.1 kJ/mol-atom ± 4.6 | 298.15 | experimental | -75.502 (mp-aaaaaboc) | -79.13 (oqmd-647082) | [2] Zhao 2000; _cites Golutvin 1971_ | Table 3, p. 3, row 12; `ORC-VWFCJHEUZJ.3fa291` |  |
| HfSi | [HfSi](https://data.orchid-project.org/compounds/HfSi.html) | -70.9 kJ/mol-atom ± 2 | 1473 | experimental | -75.502 (mp-aaaaaboc) | -79.13 (oqmd-647082) | [2] Zhao 2000; _cites Meschel 1998_ [doi](https://doi.org/10.1016/s0925-8388%2898%2900747-6) | Table 3, p. 3, row 15; `ORC-SYPHVE2N5D.50bf91` |  |

## Other properties

### Phase transition (2)

Table: Phase transition, Hf–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 2753.15 K | 2753.15 | congruent melting: L -> Hf3Si2; _L: Si 0.4; Hf3Si2: Si 0.4_ | model | [2] Zhao 2000 | Table 2, p. 2, row 12; `ORC-AH3TB4CK4N` |  |
| Phase transition | 2753.15 K | 2753.15 | congruent melting: L -> Hf3Si2; _L: Si 0.4; Hf3Si2: Si 0.4_ | experimental | [2] Zhao 2000; _cites ref. 68Bru_ | Table 2, p. 2, row 11; `ORC-T4PPS65GF3` |  |

### Phase equilibrium (1)

Table: Phase equilibrium, Hf–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase assemblage |  | 2223.15 | Hf5Si3 + Hf2Si; _alloy: Si 0.35_ | experimental | [2] Zhao 2000 | p. 3; `ORC-G7OCTBZQ7T` | “The microstructure of the Hf-35at.%Si annealed at 1950 °C consisted mostly of the Hf5Si3 and Hf2Si, as shown in Fig. 2.” |

### Crystal structure (14)

Table: Crystal structure, Hf–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Lattice a | 6.553 Å | 298.15 | Hf2Si; _alloy: Si 0.333333_ | unspecified | [2] Zhao 2000; _cites Havinga 1972_ [doi](https://doi.org/10.1016/0022-5088%2872%2990028-8) | Table 1, p. 2, row 1; `ORC-QURHNRN32W.971e92` |  |
| Lattice a | 6.988 Å | 298.15 | Hf3Si2; _alloy: Si 0.4_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 3; `ORC-N7V7YNMRQS.067a6f` |  |
| Lattice a | 7.844 Å | 298.15 | Hf5Si3; _alloy: Si 0.375_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 2; `ORC-JBIGLWPGTE.851967` |  |
| Lattice a | 7.039 Å | 298.15 | Hf5Si4; _alloy: Si 0.444444_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 4; `ORC-TDVCQMAIPA.495127` |  |
| Lattice a | 6.889 Å | 298.15 | HfSi; _alloy: Si 0.5_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 5; `ORC-JW6RU27GDG.e74c81` |  |
| Lattice a | 3.672 Å | 298.15 | HfSi2; _alloy: Si 0.666667_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 6; `ORC-PLBJO2DIH6.8e0087` |  |
| Lattice b | 3.772 Å | 298.15 | HfSi; _alloy: Si 0.5_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 5; `ORC-JW6RU27GDG.e67b3c` |  |
| Lattice b | 14.57 Å | 298.15 | HfSi2; _alloy: Si 0.666667_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 6; `ORC-PLBJO2DIH6.7a5961` |  |
| Lattice c | 5.186 Å | 298.15 | Hf2Si; _alloy: Si 0.333333_ | unspecified | [2] Zhao 2000; _cites Havinga 1972_ [doi](https://doi.org/10.1016/0022-5088%2872%2990028-8) | Table 1, p. 2, row 1; `ORC-QURHNRN32W.b85c2e` |  |
| Lattice c | 3.675 Å | 298.15 | Hf3Si2; _alloy: Si 0.4_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 3; `ORC-N7V7YNMRQS.7ee8eb` |  |
| Lattice c | 5.492 Å | 298.15 | Hf5Si3; _alloy: Si 0.375_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 2; `ORC-JBIGLWPGTE.479c1a` |  |
| Lattice c | 12.83 Å | 298.15 | Hf5Si4; _alloy: Si 0.444444_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 4; `ORC-TDVCQMAIPA.74b563` |  |
| Lattice c | 5.223 Å | 298.15 | HfSi; _alloy: Si 0.5_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 5; `ORC-JW6RU27GDG.d5a4d3` |  |
| Lattice c | 3.641 Å | 298.15 | HfSi2; _alloy: Si 0.666667_ | unspecified | [2] Zhao 2000; _cites Karpinsky 1969_ | Table 1, p. 2, row 6; `ORC-PLBJO2DIH6.09b99c` |  |

## Sources

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

1. Y Yang, Y.A Chang, J.-C Zhao, B.P Bewlay, Thermodynamic modeling of the Nb–Hf–Si ternary system, Intermetallics 11, 407-415 (2003). [doi:10.1016/s0966-9795(03)00021-9](https://doi.org/10.1016/s0966-9795%2803%2900021-9)
2. J. -C. Zhao, B. P. Bewlay, M. R. Jackson, Q. Chen, Hf-Si binary phase diagram determination and thermodynamic modeling, JPE 21, 40-45 (2000). [doi:10.1361/105497100770340408](https://doi.org/10.1361/105497100770340408)

## 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/).