# Ca–O–Si system

> Ca–O–Si system: 111 accepted literature values (heat capacity / entropy / enthalpy 53, formation 26, invariant reaction 26, activity / EMF / Gibbs energy 4) and 0 calculated phase diagram(s) from ORCHID, each value with evidence class, source, page and quote.

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111 accepted literature values from 1 paper(s) (experimental 51, model 49, DFT 7, unspecified 4); 0 calculated phase diagram(s).

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Table: Accepted values by evidence class

| Evidence class | Values |
|---|---:|
| experimental | 51 |
| model | 49 |
| DFT | 7 |
| unspecified | 4 |

Table: Accepted values by property group

| Property group | Values |
|---|---:|
| invariant reaction | 26 |
| phase transition | 2 |
| formation | 26 |
| heat capacity / entropy / enthalpy | 53 |
| activity / EMF / Gibbs energy | 4 |

## Invariant reactions (literature)

Table: Invariant reactions reported in the literature for the Ca–O–Si system (26)

| T (K) | Reaction / phases | Compositions (mole fraction) | Class | Source | Location | Quote |
|---:|---|---|---|---|---|---|
| 2430 | peritectic: Liquid + CaO -> Ca3SiO5 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 13; `ORC-UREZE4ROG7` |  |
| 2423 | peritectic: Liquid + CaO -> Ca3SiO5 |  | experimental | [1] Abdul 2023; _cites Levin 1964_ | Table 9, p. 9, row 14; `ORC-ETXZ66II6M` |  |
| 2403 | congruent melting: α-Ca2SiO4 |  | experimental | [1] Abdul 2023; _cites Rankin 1915_ [doi](https://doi.org/10.2475/ajs.s4-39.229.1) | Table 9, p. 9, row 24; `ORC-FMQSFZRWUX` |  |
| 2371 | congruent melting: α-Ca2SiO4 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 23; `ORC-WJABXBSM4Y` |  |
| 2323 | eutectic: Liquid -> Ca3SiO5 + α-Ca2SiO4 |  | experimental | [1] Abdul 2023; _cites Levin 1964_ | Table 9, p. 9, row 16; `ORC-XI7672DL65` |  |
| 2300 | eutectic: Liquid -> Ca3SiO5 + α-Ca2SiO4 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 15; `ORC-4RSLIV2MF3` |  |
| 1840 | congruent melting: cyclo-CaSiO3 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 25; `ORC-VVEQXHFFRT` |  |
| 1817 | congruent melting: cyclo-CaSiO3 |  | experimental | [1] Abdul 2023 | Table 9, p. 9, row 26; `ORC-VOJWVSH7Q7` |  |
| 1741 | peritectic: Liquid + α-Ca2SiO4 -> Ca3Si2O7 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 17; `ORC-2A6TCWW62P` |  |
| 1737 | peritectic: Liquid + α-Ca2SiO4 -> Ca3Si2O7 |  | experimental | [1] Abdul 2023; _cites Levin 1964_ | Table 9, p. 9, row 18; `ORC-3YHFAYW2ZO` |  |
| 1734 | eutectic: Liquid -> Ca3Si2O7 + CaSiO3 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 19; `ORC-JG4MEUU2SO` |  |
| 1733 | eutectic: Liquid -> Ca3Si2O7 + CaSiO3 |  | experimental | [1] Abdul 2023; _cites Levin 1964_ | Table 9, p. 9, row 20; `ORC-JKVKKHTGO3` |  |
| 1710 | other: α′-Ca2SiO4 -> α-Ca2SiO4 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 5; `ORC-KSHRHIVBXY` |  |
| 1710 | other: α′-Ca2SiO4 -> α-Ca2SiO4 |  | experimental | [1] Abdul 2023; _cites Bredig 1950_ | Table 9, p. 9, row 6; `ORC-ZKM6Y4L3JC` |  |
| 1709 | eutectic: Liquid -> SiO2 + CaSiO3 |  | experimental | [1] Abdul 2023; _cites Levin 1964_ | Table 9, p. 9, row 22; `ORC-MBFED7QYTK` |  |
| 1700 | eutectic: Liquid -> SiO2 + CaSiO3 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 21; `ORC-AREY5MK6WT` |  |
| 1398 | other: Wollastonite -> cyclo-CaSiO3 |  | experimental | [1] Abdul 2023; _cites Voronko 2002_ | Table 9, p. 9, row 8; `ORC-YMKXGKFAVA` |  |
| 1397 | other: Wollastonite -> cyclo-CaSiO3 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 7; `ORC-E3ORTPQG73` |  |
| 1323 | other: Monoclinic -> rhombohedral-Ca3SiO5 |  | experimental | [1] Abdul 2023; _cites Bigare_ | Table 9, p. 9, row 12; `ORC-DVZDXIDJYM` |  |
| 1317 | other: Monoclinic -> rhombohedral-Ca3SiO5 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 11; `ORC-7QNDERCAEI` |  |
| 1254 | other: Triclinic -> monoclinic-Ca3SiO5 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 9; `ORC-WPD6JF364P` |  |
| 1253 | other: Triclinic -> monoclinic-Ca3SiO5 |  | experimental | [1] Abdul 2023; _cites Bigare_ | Table 9, p. 9, row 10; `ORC-BQDQGKDHNF` |  |
| 1120 | other: γ-Ca2SiO4 -> α′-Ca2SiO4 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 1; `ORC-ACJKMYZYV4` |  |
| 1120 | other: γ-Ca2SiO4 -> α′-Ca2SiO4 |  | experimental | [1] Abdul 2023; _cites Bredig 1950_ | Table 9, p. 9, row 2; `ORC-JILLMS7XRG` |  |
| 970 | other: β-Ca2SiO4 -> α′-Ca2SiO4 |  | model | [1] Abdul 2023 | Table 9, p. 9, row 3; `ORC-QXBWONLLY6` |  |
| 970 | other: β-Ca2SiO4 -> α′-Ca2SiO4 |  | experimental | [1] Abdul 2023; _cites Bredig 1950_ | Table 9, p. 9, row 4; `ORC-U4OYNO5WKJ` |  |

## 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, Ca–O–Si system (19)

| Phase | Compound | Value | T (K) | Class | MP DFT (kJ/mol-atom) | OQMD DFT (kJ/mol-atom) | Source | Location | Quote |
|---|---|---:|---:|---|---:|---:|---|---|---|
| Cyclowollastonite-CaSiO3 |  | -1627 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 10; `ORC-D24CXWORIZ.1ee8ea` |  |
| Cyclowollastonite-CaSiO3 |  | -1627 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 9; `ORC-LNOSS6BP7G.989c1b` |  |
| Monoclinic-Ca3SiO5 |  | -2932 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 1; `ORC-LR3E2JWMCJ.c2bd75` |  |
| Rankinite-Ca3Si2O7 |  | -3973 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 6; `ORC-DPJJOCX34T.4f120f` |  |
| Rankinite-Ca3Si2O7 |  | -3951 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 5; `ORC-YAPGGLBFMB.27d8c3` |  |
| Rhombohedral-Ca3SiO5 |  | -2932 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 4; `ORC-MBGJUXIP4S.741729` |  |
| Triclinic-Ca3SiO5 |  | -2933 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 3; `ORC-JROABWBD6S.061fb2` |  |
| Triclinic-Ca3SiO5 |  | -2933 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 2; `ORC-SVDSIHBID2.df2c38` |  |
| Wollastonite-CaSiO3 |  | -1634 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 8; `ORC-FJQUPO45FZ.d695f3` |  |
| Wollastonite-CaSiO3 |  | -1634 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 7; `ORC-QVLNEA5VP5.ef9a1d` |  |
| wollastonite-CaSiO3 |  | -1634.32 kJ/mol (basis unstated) ± 2.71 | 298.15 | unspecified |  |  | [1] Abdul 2023; _cites Grevel 2022_ | Table A.2, p. 13, row 21; `ORC-JHG5GVRDTR` |  |
| α-Ca2SiO4 |  | -2548 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 12; `ORC-QQR4UGT3GS.ad28d4` |  |
| α-Ca2SiO4 |  | -2293 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 11; `ORC-AMXBRCNROZ.9789a9` |  |
| α′-Ca2SiO4 |  | -2304 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 13; `ORC-DOD36BIQRQ.dd12cd` |  |
| α′-Ca2SiO4 |  | -2198 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 14; `ORC-PBAHCHHFYE.0275fc` |  |
| β-Ca2SiO4 |  | -2307 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 15; `ORC-ETBEBYX5XW.89fdb7` |  |
| β-Ca2SiO4 |  | -2306 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 16; `ORC-3QNEW2TV5R.e38ae3` |  |
| γ-Ca2SiO4 |  | -2316 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023 | Table 7, p. 8, row 17; `ORC-N4E76HFI6M.5129ec` |  |
| γ-Ca2SiO4 |  | -2316 kJ/mol (basis unstated) | 298.15 | model |  |  | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 18; `ORC-RFZ5DTDIVY.160aa4` |  |

## Other properties

### Phase transition (2)

Table: Phase transition, Ca–O–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Phase transition | 1295.15 K | 1295.15 | polymorphic: Kilch → rank; _alloy: O 0.583333, Si 0.166667_ | unspecified | [1] Abdul 2023; _cites Hanic 1987_ | Table 2, p. 2, row 20; `ORC-MOZZUSVQ2O` |  |
| Phase transition | 1398.15 K | 1398.15 | polymorphic: Woll → p-woll; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites Voronko 2002_ | Table 2, p. 2, row 21; `ORC-TQ36AVTVMT` |  |

### Formation (7)

Table: Formation, Ca–O–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| hm from compounds; _printed: Efor(0 K)_ | -17.6667 kJ/mol-atom | 0 | Ca3Si2O7; _alloy: O 0.583333, Si 0.166667_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 5; `ORC-7KM7ES5UHY.a50fc1` |  |
| hm from compounds; _printed: Efor(0 K)_ | -15.5 kJ/mol-atom | 0 | CaSiO3-cyclowollastonite; _alloy: O 0.6, Si 0.2_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 7; `ORC-DYZ2DGOTA6.0e7594` |  |
| hm from compounds; _printed: Efor(0 K)_ | -17.14 kJ/mol-atom | 0 | CaSiO3-wollastonite; _alloy: O 0.6, Si 0.2_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 6; `ORC-UXGF5MWXGO.1fb16b` |  |
| hm from compounds; _printed: Efor_ | -13.1 kJ/mol-atom | 0 | Monoclinic-Ca3SiO5; _alloy: O 0.555556, Si 0.111111_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 1; `ORC-QCP6QIK2KF.6d086b` |  |
| hm from compounds; _printed: Efor_ | -17.4857 kJ/mol-atom | 0 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 4; `ORC-YFT6HW55OB.a24bba` |  |
| hm from compounds; _printed: Efor_ | -17.8286 kJ/mol-atom | 0 | β-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 3; `ORC-4AIBGJKEWA.ef9a26` |  |
| hm from compounds; _printed: Efor_ | -18.7429 kJ/mol-atom | 0 | γ-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | DFT | [1] Abdul 2023 | Table 6, p. 8, row 2; `ORC-NV32G2F3H2.5adccd` |  |

### Heat capacity / entropy / enthalpy (53)

Table: Heat capacity / entropy / enthalpy, Ca–O–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Entropy; _printed: S298_ | 87.2 J/mol (basis unstated)/K | 298.15 | Cyclowollastonite-CaSiO3 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 10; `ORC-D24CXWORIZ.6cd51d` |  |
| Entropy; _printed: S298_ | 87.6 J/mol (basis unstated)/K | 298.15 | Cyclowollastonite-CaSiO3 | model | [1] Abdul 2023 | Table 7, p. 8, row 9; `ORC-LNOSS6BP7G.9bf523` |  |
| Entropy; _printed: S298_ | 166.4 J/mol (basis unstated)/K | 298.15 | Monoclinic-Ca3SiO5 | model | [1] Abdul 2023 | Table 7, p. 8, row 1; `ORC-LR3E2JWMCJ.598aa1` |  |
| Entropy; _printed: S298_ | 210.6 J/mol (basis unstated)/K | 298.15 | Rankinite-Ca3Si2O7 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 6; `ORC-DPJJOCX34T.7f9689` |  |
| Entropy; _printed: S298_ | 207.6 J/mol (basis unstated)/K | 298.15 | Rankinite-Ca3Si2O7 | model | [1] Abdul 2023 | Table 7, p. 8, row 5; `ORC-YAPGGLBFMB.c43f49` |  |
| Entropy; _printed: S298_ | 166.4 J/mol (basis unstated)/K | 298.15 | Rhombohedral-Ca3SiO5 | model | [1] Abdul 2023 | Table 7, p. 8, row 4; `ORC-MBGJUXIP4S.7e1553` |  |
| Entropy; _printed: S298_ | 168.6 J/mol (basis unstated)/K | 298.15 | Triclinic-Ca3SiO5 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 3; `ORC-JROABWBD6S.d7ada1` |  |
| Entropy; _printed: S298_ | 166.5 J/mol (basis unstated)/K | 298.15 | Triclinic-Ca3SiO5 | model | [1] Abdul 2023 | Table 7, p. 8, row 2; `ORC-SVDSIHBID2.c72517` |  |
| Entropy; _printed: S298_ | 81 J/mol (basis unstated)/K | 298.15 | Wollastonite-CaSiO3 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 8; `ORC-FJQUPO45FZ.b10135` |  |
| Entropy; _printed: S298_ | 79.6 J/mol (basis unstated)/K | 298.15 | Wollastonite-CaSiO3 | model | [1] Abdul 2023 | Table 7, p. 8, row 7; `ORC-QVLNEA5VP5.e9a9ca` |  |
| Entropy; _printed: S298_ | 132.7 J/mol (basis unstated)/K | 298.15 | α-Ca2SiO4 | model | [1] Abdul 2023 | Table 7, p. 8, row 11; `ORC-AMXBRCNROZ.f502b7` |  |
| Entropy; _printed: S298_ | 84.91 J/mol (basis unstated)/K | 298.15 | α-Ca2SiO4 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 12; `ORC-QQR4UGT3GS.b1ffe5` |  |
| Entropy; _printed: S298_ | 130.4 J/mol (basis unstated)/K | 298.15 | α′-Ca2SiO4 | model | [1] Abdul 2023 | Table 7, p. 8, row 13; `ORC-DOD36BIQRQ.3e63bb` |  |
| Entropy; _printed: S298_ | 116 J/mol (basis unstated)/K | 298.15 | α′-Ca2SiO4 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 14; `ORC-PBAHCHHFYE.3df2c2` |  |
| Entropy; _printed: S298_ | 126.7 J/mol (basis unstated)/K | 298.15 | β-Ca2SiO4 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 16; `ORC-3QNEW2TV5R.50027f` |  |
| Entropy; _printed: S298_ | 126.1 J/mol (basis unstated)/K | 298.15 | β-Ca2SiO4 | model | [1] Abdul 2023 | Table 7, p. 8, row 15; `ORC-ETBEBYX5XW.f3f23f` |  |
| Entropy; _printed: S298_ | 119 J/mol (basis unstated)/K | 298.15 | γ-Ca2SiO4 | model | [1] Abdul 2023 | Table 7, p. 8, row 17; `ORC-N4E76HFI6M.f0561b` |  |
| Entropy; _printed: S298_ | 120.5 J/mol (basis unstated)/K | 298.15 | γ-Ca2SiO4 | model | [1] Abdul 2023; _cites Haas 1981_ [doi](https://doi.org/10.1063/1.555645) | Table 7, p. 8, row 18; `ORC-RFZ5DTDIVY.059e41` |  |
| Heat capacity; _printed: Cp_ | 0.192 J/mol (basis unstated)/K ± 0.02 | 156.805 | wollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites Wagner 1932_ [doi](https://doi.org/10.1002/zaac.19322080102) | Table A.2, p. 13, row 15; `ORC-UXMHHNYWV4` |  |
| Heat capacity; _printed: Cp_ | 29.6 J/mol (basis unstated)/K ± 0.28 | 175.8 | rankinite-Ca3Si2O7; _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023; _cites King 1957_ [doi](https://doi.org/10.1021/ja01577a028) | Table A.2, p. 13, row 9; `ORC-DAMLJ4NSYI` |  |
| Heat capacity; _printed: Cp_ | 97.4 J/mol (basis unstated)/K ± 1 | 773.2 | wollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites Wagner 1932_ [doi](https://doi.org/10.1002/zaac.19322080102) | Table A.2, p. 13, row 16; `ORC-EZB37CIS52` |  |
| Heat capacity; _printed: Cp_ | 0.22 J/mol (basis unstated)/K ± 0.01 | 791.95 | cyclowollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites Wagner 1932_ [doi](https://doi.org/10.1002/zaac.19322080102) | Table A.2, p. 13, row 23; `ORC-BNS42AA4MP` |  |
| Heat capacity; _printed: Cp_ | 95.81 J/mol (basis unstated)/K ± 1 | 973.2 | cyclowollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites Wagner 1932_ [doi](https://doi.org/10.1002/zaac.19322080102) | Table A.2, p. 13, row 24; `ORC-NLUPCUXYP2` |  |
| Heat content; _printed: HT-H298K_ | 147433 J mol−1 K−1 ± 3570.3 | 872.45 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 2; `ORC-DSVMSUFNI2.853b28` |  |
| Heat content; _printed: HT-H298K_ | 147433 J mol-1 K-1 ± 3570.3 | 872.45 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 2; `ORC-DSVMSUFNI2.ade0ba` |  |
| Heat content; _printed: HT-H298K_ | 108431 J mol-1 ± 3617.9 | 972.86 | γ-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 2; `ORC-BMBRKUTEX2.d863e6` |  |
| Heat content; _printed: HT-H298K_ | 108431 J mol^-1 ± 3617.9 | 972.86 | γ-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 2; `ORC-BMBRKUTEX2.e8cc12` |  |
| Heat content; _printed: HT-H298K_ | 180037 J mol−1 K−1 ± 4109.9 | 972.95 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 3; `ORC-MYYX7E63YF.1e7051` |  |
| Heat content; _printed: HT-H298K_ | 180037 J mol-1 K-1 ± 4109.9 | 972.95 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 3; `ORC-MYYX7E63YF.3fc5c0` |  |
| Heat content; _printed: HT-H298K_ | 123307 J mol-1 ± 3251.5 | 1072.09 | γ-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 3; `ORC-IT6TAZ3EWE.5027f8` |  |
| Heat content; _printed: HT-H298K_ | 123307 J mol^-1 ± 3251.5 | 1072.09 | γ-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 3; `ORC-IT6TAZ3EWE.ac8465` |  |
| Heat content; _printed: HT-H298K_ | 206086 J mol−1 K−1 ± 5517.3 | 1072.35 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 4; `ORC-U5RWJ64D7G.b5cc16` |  |
| Heat content; _printed: HT-H298K_ | 206086 J mol-1 K-1 ± 5517.3 | 1072.35 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 4; `ORC-U5RWJ64D7G.9f0664` |  |
| Heat content; _printed: HT-H298K_ | 148802 J mol-1 ± 3879.2 | 1171.39 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 4; `ORC-WFAGEJZWN4.37db15` |  |
| Heat content; _printed: HT-H298K_ | 148802 J mol^-1 ± 3879.2 | 1171.39 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 4; `ORC-WFAGEJZWN4.e864e5` |  |
| Heat content; _printed: HT - H298.15_ | 148229 J mol^-1 ± 3574.7 | 1172.05 | rankinite-Ca3Si2O7; _alloy: O 0.583333, Si 0.166667_ | unspecified | [1] Abdul 2023 | Table A.2, p. 13, row 10; `ORC-RCPU7RZXHA` |  |
| Heat content; _printed: HT-H298K_ | 233440 J mol−1 K−1 ± 6032.1 | 1172.15 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 5; `ORC-2JFX3ENSPU.b77cc5` |  |
| Heat content; _printed: HT-H298K_ | 233440 J mol-1 K-1 ± 6032.1 | 1172.15 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 5; `ORC-2JFX3ENSPU.595a1d` |  |
| Heat content; _printed: HT-H298K_ | 171305 J mol-1 ± 4185.5 | 1271.67 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 5; `ORC-CGUMDXY3GC.bc6a9e` |  |
| Heat content; _printed: HT-H298K_ | 171305 J mol^-1 ± 4185.5 | 1271.67 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 5; `ORC-CGUMDXY3GC.e42274` |  |
| Heat content; _printed: HT-H298K_ | 264147 J mol−1 K−1 ± 6983.6 | 1271.95 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 6; `ORC-S6DB6FEWKT.e40486` |  |
| Heat content; _printed: HT-H298K_ | 264147 J mol-1 K-1 ± 6983.6 | 1271.95 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 6; `ORC-S6DB6FEWKT.cb43f3` |  |
| Heat content; _printed: HT-H298K_ | 293304 J mol−1 K−1 ± 7690.3 | 1370.85 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 7; `ORC-I7VLW5NRKT.5c2813` |  |
| Heat content; _printed: HT-H298K_ | 293304 J mol-1 K-1 ± 7690.3 | 1370.85 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 7; `ORC-I7VLW5NRKT.745546` |  |
| Heat content; _printed: HT-H298K_ | 187890 J mol^-1 ± 4479.1 | 1371.05 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 6; `ORC-TOX2L54ZAP.502275` |  |
| Heat content; _printed: HT-H298K_ | 187890 J mol-1 ± 4479.1 | 1371.05 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 6; `ORC-TOX2L54ZAP.c19639` |  |
| Heat content; _printed: HT-H298K_ | 212360 J mol-1 ± 6444.6 | 1471.05 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 7; `ORC-5AEJOMPQVX.0ae1b9` |  |
| Heat content; _printed: HT-H298K_ | 212360 J mol^-1 ± 6444.6 | 1471.05 | α′-Ca2SiO4; _alloy: O 0.571429, Si 0.142857_ | experimental | [1] Abdul 2023 | Table 4, p. 7, row 7; `ORC-5AEJOMPQVX.c7a7b8` |  |
| Heat content; _printed: HT-H298K_ | 322841 J mol−1 K−1 ± 6913.1 | 1471.65 | Ca3Si2O7 (Rankinite); _alloy: O 0.583333, Si 0.166667_ | experimental | [1] Abdul 2023 | Table 3, p. 7, row 8; `ORC-ZY2AV66DJM.c1b04e` |  |
| Heat content; _printed: HT-H298K_ | 322841 J mol-1 K-1 ± 6913.1 | 1471.65 | Rankinite | experimental | [1] Abdul 2023 | Table 3, p. 7, row 8; `ORC-ZY2AV66DJM.e98f82` |  |
| heat content from base t; _printed: HT - H293.15_ | 28503.1 J mol^-1 ± 761 | 973.15 | wollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites H 1933_ | Table A.2, p. 13, row 17; `ORC-GMY76YUVXV` |  |
| heat content from base t; _printed: HT - H273.15_ | 57803 J mol^-1 ± 2000 | 1152.4 | cyclowollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | unspecified | [1] Abdul 2023; _cites Richet 1991_ [doi](https://doi.org/10.1029/90jb02172) | Table A.2, p. 13, row 25; `ORC-O666O3ZHIX` |  |
| heat content from base t; _printed: HT - H273.15_ | 92588 J mol^-1 ± 2000 | 1454.4 | cyclowollastonite-CaSiO3; _alloy: O 0.6, Si 0.2_ | experimental | [1] Abdul 2023; _cites Courtial 2000_ [doi](https://doi.org/10.1007/s002690050253) | Table A.2, p. 13, row 26; `ORC-QZETOYXSHJ` |  |

### Activity / EMF / Gibbs energy (4)

Table: Activity / EMF / Gibbs energy, Ca–O–Si system

| Property | Value | T (K) | Phases / composition | Class | Source | Location | Quote |
|---|---:|---:|---|---|---|---|---|
| Gibbs energy; _printed: ΔG_ | 10999.3 J mol^-1 ± 771.88 | 953 | UNKNOWN | experimental | [1] Abdul 2023; _cites Benz 1961_ [doi](https://doi.org/10.1021/j100826a007) | Table A.2, p. 13, row 11; `ORC-OIAZR5S46X` |  |
| Gibbs energy; _printed: ΔG_ | 80082.8 J mol^-1 ± 1157.82 | 973.15 | UNKNOWN | experimental | [1] Abdul 2023; _cites Benz 1961_ [doi](https://doi.org/10.1021/j100826a007) | Table A.2, p. 13, row 29; `ORC-AMNAGVF63R` |  |
| Gibbs energy; _printed: ΔG_ | 88380.6 J mol^-1 ± 771.88 | 1023.15 | UNKNOWN | experimental | [1] Abdul 2023; _cites Benz 1961_ [doi](https://doi.org/10.1021/j100826a007) | Table A.2, p. 13, row 22; `ORC-CUAWRJ4LGQ` |  |
| Gibbs energy; _printed: ΔG_ | 11192.3 J mol^-1 ± 771.88 | 1057 | UNKNOWN | experimental | [1] Abdul 2023; _cites Benz 1961_ [doi](https://doi.org/10.1021/j100826a007) | Table A.2, p. 13, row 12; `ORC-ELB3PYE56N` |  |

## Sources

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

1. Wahab Abdul, Chancel Mawalala, Alexander Pisch, Marcus Nigel Bannerman, CaO-SiO2 assessment using 3rd generation CALPHAD models, Cement and Concrete Research 173, 107309 (2023). [doi:10.1016/j.cemconres.2023.107309](https://doi.org/10.1016/j.cemconres.2023.107309)

## 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 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_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/).