Si2Ta: enthalpy of formation

12 accepted literature formation-enthalpy value(s) (experimental 8, model 3, unspecified 1); experimental median -39.25 kJ/mol-atom (n = 8); Materials Project -41.496 kJ/mol-atom (mp-aaaaaqom); OQMD -46.105 kJ/mol-atom (oqmd-8153).

Systems: Si–Ta

Literature values

Enthalpy of formation of Si2Ta reported in the literature (12)
Value	Phase as printed	T (K)	Class	Method	System	Source	Location
-46 kJ/mol-atom ± 2.5	TaSi2	298.15	experimental		Si–Ta	[1] Broz 2013 cites Meschel 1998 doi	Table 2, p. 6, row 45 report
-46 kJ/mol-atom ± 2.5	Si0.6667Ta0.3333	1473	experimental	DSC.	Si–Ta	[2] Drouelle 2013 cites Meschel 1998 doi	Table 2, p. 2, row 7 report
-43.332 kJ/mol-atom	Si0.6667Ta0.3333	1760.5	experimental	Kundsen eff. Method	Si–Ta	[2] Drouelle 2013 cites Myers 1957 doi	Table 2, p. 2, row 4 report
-39.7 kJ/mol-atom	Si0.6667Ta0.3333	298.15	experimental	Method unknown	Si–Ta	[2] Drouelle 2013 cites Kubaschewski 1968	Table 2, p. 2, row 3 report
-38.8 kJ/mol-atom	Si0.6667Ta0.3333	298.15	experimental	Calorimetric method	Si–Ta	[2] Drouelle 2013 cites Robins 1955 doi	Table 2, p. 2, row 2 report
-38.8 kJ/mol-atom	TaSi2	298.15	experimental		Si–Ta	[1] Broz 2013 cites Robins 1955 doi	Table 2, p. 6, row 47 report
-32.4 kJ/mol-atom ± 14	TaSi2	298.15	experimental		Si–Ta	[1] Broz 2013 cites Myers 1957	Table 2, p. 6, row 44 report
-22.6 kJ/mol-atom ± 7.8	TaSi2	298.15	experimental		Si–Ta	[1] Broz 2013 cites Levine 1969 doi	Table 2, p. 6, row 46 report
-46.0991 kJ/mol-atom	Si0.6667Ta0.3333	298.15	model	Optimization	Si–Ta	[2] Drouelle 2013	Table 2, p. 2, row 6 report
-44 kJ/mol-atom	Si0.6667Ta0.3333	298.15	model	Prediction	Si–Ta	[2] Drouelle 2013 cites F 1988	Table 2, p. 2, row 5 report
-41.1 kJ/mol-atom	TaSi2	0	model		Si–Ta	[1] Broz 2013 cites Guo 2009 doi	Table 2, p. 6, row 48 report
-46.7 kJ/mol-atom	TaSi2	0	unspecified		Si–Ta	[1] Broz 2013	Table 2, p. 6, row 43 report

Uncertainty budget

Components kept separate, in the value's unit (literature SCHEMA.md, UNCERTAINTY_CALIBRATION.md): effective = max(sqrt(max(printed, reading, method)^2 + composition^2 + conversion^2), scatter). The method floor is the robust between-study scatter of the method class in ORCHID (calibrated) or a documented prior; printed values and printed uncertainties are unchanged.

Uncertainty budget of the literature values of Si2Ta
Value	Unit	Printed	Reading	Method (class, basis)	Effective
-46	kJ/mol-atom	2.5	0.05	3.5 (unknown, calibrated)	3.5
-46	kJ/mol-atom	2.5	5.000e-5	2 (dsc_dta, prior)	2.5
-43.332	kJ/mol-atom		5.000e-5	4.2 (kems_vapour, calibrated)	4.2
-39.7	kJ/mol-atom		5.000e-4	4.1 (experimental_unspecified, cleaned_below_threshold)	4.1
-38.8	kJ/mol-atom		5.000e-4	3.2 (solution_reaction_calorimetry, calibrated)	3.2
-38.8	kJ/mol-atom		0.05	3.5 (unknown, calibrated)	3.5
-32.4	kJ/mol-atom	14	0.05	3.5 (unknown, calibrated)	14
-22.6	kJ/mol-atom	7.8	0.05	3.5 (unknown, calibrated)	7.8
-46.0991	kJ/mol-atom		5.000e-8	3.9 (model_calculated, calibrated)	3.9
-44	kJ/mol-atom		5.000e-4	3.9 (model_calculated, calibrated)	3.9
-41.1	kJ/mol-atom		0.05	3.9 (model_calculated, calibrated)	3.9
-46.7	kJ/mol-atom		0.05	3.5 (unknown, calibrated)	3.5

DFT formation energies

Lowest-energy entries at this composition. Materials Project and OQMD use different energy references and are never averaged. 1 eV/atom = 96.485 kJ/mol-atom.

DFT formation energy of Si2Ta
Source	Entry	kJ/mol-atom	eV/atom	Space group	E above hull (kJ/mol-atom)	E above hull (eV/atom)	Theoretical
Materials Project	mp-aaaaaqom	-41.496	-0.430078	P6_422	0	0	no
OQMD	oqmd-8153	-46.105	-0.477847	P6222	0	0	no

DFT sources: A. Jain et al., Commentary: The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002. doi:10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501-1509; S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010. doi:10.1007/s11837-013-0755-4 (CC BY 4.0);

Sources

P. Broz, A.U. Khan, H. Niu, X.-Q. Chen, D. Li, J. Vrestal et al., The system Ta–V–Si: Thermodynamic modeling, Journal of Solid State Chemistry 199, 171-180 (2013). doi:10.1016/j.jssc.2012.12.003
I. Drouelle, C. Servant, Thermodynamic assessment of the Si–Ta system, Journal of Alloys and Compounds 551, 293-299 (2013). doi:10.1016/j.jallcom.2012.09.148

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). doi:10.5281/zenodo.23735569
R. Arróyave, J. Saal, D. Shin, ORCHID-Parity: DFT-vs-experiment formation-enthalpy benchmark (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23735943
R. Arróyave, J. Saal, D. Shin, ORCHID data: umbrella record of the ORCHID datasets (version 2026.10; Version 1, machine-extracted), Zenodo (2026). doi:10.5281/zenodo.23736065

Also cite the original source of every value you use (paper_citation / paper_doi, and cited_dois for values the paper cites from earlier work); 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); G. Kim, S. V. Meschel, P. Nash, W. Chen, Experimental formation enthalpies for intermetallic phases and other inorganic compounds, Scientific Data 4 (2017) 170162, https://doi.org/10.1038/sdata.2017.162; 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. Version 1, machine-extracted: values were read by language-model readers constrained to quote their source and checked automatically, and the release was then audited on the printed pages by adversarial audits, an independent second review of fit-facing records and a preliminary human review of a frozen sample. Flags such as accepted and ESPEI-ready record screening results, not certification; known issues are listed in the release notes.

@misc{orchid_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_dft_benchmark_2026,
  author    = {Arr{\'o}yave, Raymundo and Saal, James and Shin, Dongwon},
  title     = {{ORCHID-Parity: DFT-vs-experiment formation-enthalpy benchmark}},
  version   = {2026.10},
  publisher = {Zenodo},
  year      = {2026},
  doi       = {10.5281/zenodo.23735943},
  url       = {https://doi.org/10.5281/zenodo.23735943},
  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}
}