Selected ATcT [1, 2] enthalpy of formation based on version 1.148 of the Thermochemical Network [3]

This version of ATcT results[3] was generated by additional expansion of version 1.140 to include species relevant to a recent study of the role of atmospheric methanediol[4].

Dioxosilane

Formula: SiO2 (cr, cristobalite)

CAS RN: 7631-86-9

ATcT ID: 7631-86-9*510

SMILES: O=[Si]=O

InChI: InChI=1S/O2Si/c1-3-2

InChIKey: VYPSYNLAJGMNEJ-UHFFFAOYSA-N

Hills Formula: O2Si1

2D Image:

Aliases: SiO2; Dioxosilane; Silicon dioxide; Quartz; alpha-Quartz; beta-Quartz; Cristobalite; Tridymite; Aventurine; Silica; Silicon oxide; Silicon (IV) oxide; 14808-60-7; 14464-46-1; 99493-55-7; 15468-32-3; 60676-86-0

Relative Molecular Mass: 60.08430 ± 0.00067

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
-904.05	-908.91	± 0.68	kJ/mol

Top contributors to the provenance of Δ_fH° of SiO2 (cr, cristobalite)

The 17 contributors listed below account for 90.7% of the provenance of Δ_fH° of SiO2 (cr, cristobalite).

Please note: The list is limited to 20 most important contributors or, if less, a number sufficient to account for 90% of the provenance. The Reference acts as a further link to the relevant references and notes for the measurement. The Measured Quantity is normaly given in the original units; in cases where we have reinterpreted the original measurement, the listed value may differ from that given by the authors. The quoted uncertainty is the a priori uncertainty used as input when constructing the initial Thermochemical Network, and corresponds either to the value proposed by the original authors or to our estimate; if an additional multiplier is given in parentheses immediately after the prior uncertainty, it corresponds to the factor by which the prior uncertainty needed to be multiplied during the ATcT analysis in order to make that particular measurement consistent with the prevailing knowledge contained in the Thermochemical Network.

Contribution (%)	TN ID	Reaction	Measured Quantity	Reference
17.8	8198.1	Si (cr,l) + 2 F2 (g) → SiF4 (g)	Δ_rH°(298.15 K) = -385.98 ± 0.19 kcal/mol	Wise 1963, Wise 1963, Wise 1962
15.9	546.1	SiF4 (g) + 2 H2O (cr,l) → Si (cr,l) + O2 (g) + 4 HF (aq, 5 H2O)	Δ_rH°(298.15 K) = 899.77 ± 1.20 kJ/mol	Paulechka 2020, Vorobev 1960, Hummel 1959, Johnson 1987, Good 1964, Good 1964, Johnson 1973
11.6	8159.1	Si (cr,l) + O2 (g) → SiO2 (cr,l)	Δ_rH°(298.15 K) = -217.58 ± 0.35 (×1.164) kcal/mol	Good 1964, Good 1964, Good 1962, King 1951
7.4	545.1	SiF4 (g) + 2 H2O (cr,l) → SiO2 (cr, quartz) + 4 HF (aq, 5 H2O)	Δ_rH°(298.15 K) = -11.11 ± 0.37 kJ/mol	Paulechka 2020, Vorobev 1960, Hummel 1959, Johnson 1987, Good 1964, Good 1964, Kilday 1973, Kilday 1973, Johnson 1973
5.9	8200.1	SiO2 (vitr) + 2 F2 (g) → SiF4 (g) + O2 (g)	Δ_rH°(298.15 K) = -170.04 ± 0.25 kcal/mol	Wise 1963, Wise 1963
5.6	8161.3	SiO2 (cr, quartz) → SiO2 (cr, cristobalite)	Δ_rH°(347.85 K) = 0.63 ± 0.10 kcal/mol	Kracek 1953, est unc
4.9	8198.3	Si (cr,l) + 2 F2 (g) → SiF4 (g)	Δ_rH°(298.15 K) = -1615.78 ± 0.46 (×3.292) kJ/mol	Johnson 1986, Johnson 1986
4.4	8164.2	SiO2 (cr, cristobalite) → SiO2 (vitr)	Δ_rH°(347.85 K) = 1.55 ± 0.10 kcal/mol	Kracek 1953, est unc
3.2	544.2	H2O (cr,l) + F2 (g) → 2 HF (aq, 5 H2O) + 1/2 O2 (g)	Δ_rH°(298.15 K) = -356.66 ± 0.40 kJ/mol	Paulechka 2020, Johnson 1987, Vorobev 1960, Hummel 1959, Johnson 1973
2.7	8199.1	SiO2 (cr,l) + 2 F2 (g) → SiF4 (g) + O2 (g)	Δ_rH°(298.15 K) = -168.26 ± 0.28 (×1.269) kcal/mol	Wise 1963, Wise 1963
2.5	8161.2	SiO2 (cr, quartz) → SiO2 (cr, cristobalite)	Δ_rH°(970 K) = 0.45 ± 0.15 kcal/mol	Holm 1967
1.7	8141.2	Si (cr,l) → Si (g)	Δ_rG°(1525 K) = 231.1 ± 2.0 kJ/mol	Batdorf 1959, 3rd Law
1.5	8291.1	SiH3SiH3 (g) → 2 Si (cr,l) + 3 H2 (g)	Δ_rH°(298.15 K) = -19.1 ± 0.6 (×1.61) kcal/mol	Gunn 1961, est unc
1.5	545.2	SiF4 (g) + 2 H2O (cr,l) → SiO2 (cr, quartz) + 4 HF (aq, 5 H2O)	Δ_rH°(298.15 K) = -11.95 ± 0.25 (×3.221) kJ/mol	Paulechka 2020, Vorobev 1960, Hummel 1959, Johnson 1987, Good 1964, Good 1964, Johnson 1982, Johnson 1973
1.4	8255.1	SiH4 (g) → Si (cr,l) + 2 H2 (g)	Δ_rH°(298.15 K) = -8.3 ± 0.5 kcal/mol	Gunn 1961, Gurvich TPIS, est unc
1.0	8164.1	SiO2 (cr, cristobalite) → SiO2 (vitr)	Δ_rH°(970 K) = 0.95 ± 0.15 (×1.354) kcal/mol	Holm 1967
0.9	486.1	1/2 H2 (g) + 1/2 F2 (g) → HF (l)	Δ_rH°(298.15 K) = -303.56 ± 0.27 (×1.325) kJ/mol	Settle 1994, Johnson 1973, note HF

Top 10 species with enthalpies of formation correlated to the Δ_fH° of SiO2 (cr, cristobalite)

Please note: The correlation coefficients are obtained by renormalizing the off-diagonal elements of the covariance matrix by the corresponding variances.
The correlation coefficient is a number from -1 to 1, with 1 representing perfectly correlated species, -1 representing perfectly anti-correlated species, and 0 representing perfectly uncorrelated species.

Correlation Coefficent (%)	Species Name	Formula	Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units	Relative Molecular Mass	ATcT ID
92.2	Dioxosilane	SiO2 (cr, quartz)	-906.75	-911.73	± 0.63	kJ/mol	60.08430 ± 0.00067	7631-86-9*505
92.2	Dioxosilane	SiO2 (cr,l)	-906.75	-911.73	± 0.63	kJ/mol	60.08430 ± 0.00067	7631-86-9*500
91.9	Dioxosilane	SiO2 (vitr)	-826.31	-902.23	± 0.65	kJ/mol	60.08430 ± 0.00067	7631-86-9*520
65.3	Tetrafluorosilane	SiF4 (g)	-1608.76	-1614.27	± 0.52	kJ/mol	104.07911 ± 0.00030	7783-61-1*0
53.7	Oxosilylene	SiO (g)	-98.38	-97.22	± 0.54	kJ/mol	44.08490 ± 0.00042	10097-28-6*0
48.3	Silicon atom dication	[Si]+2 (g)	2813.97	2816.95	± 0.56	kJ/mol	28.08440 ± 0.00030	14175-55-4*0
48.3	Silicon cation	Si+ (g)	1236.84	1240.97	± 0.56	kJ/mol	28.08495 ± 0.00030	14067-07-3*0
48.3	Silicon anion	Si- (g)	316.25	319.23	± 0.56	kJ/mol	28.08605 ± 0.00030	14337-02-1*0
48.3	Silicon	Si (g)	450.32	454.66	± 0.56	kJ/mol	28.08550 ± 0.00030	7440-21-3*0
48.3	Silicon atom trication	[Si]+3 (g)	6045.56	6048.54	± 0.56	kJ/mol	28.08385 ± 0.00030	14175-56-5*0

Most Influential reactions involving SiO2 (cr, cristobalite)

Please note: The list, which is based on a hat (projection) matrix analysis, is limited to no more than 20 largest influences.

Influence Coefficient	TN ID	Reaction	Measured Quantity	Reference
0.407	8164.2	SiO2 (cr, cristobalite) → SiO2 (vitr)	Δ_rH°(347.85 K) = 1.55 ± 0.10 kcal/mol	Kracek 1953, est unc
0.395	8161.3	SiO2 (cr, quartz) → SiO2 (cr, cristobalite)	Δ_rH°(347.85 K) = 0.63 ± 0.10 kcal/mol	Kracek 1953, est unc
0.175	8161.2	SiO2 (cr, quartz) → SiO2 (cr, cristobalite)	Δ_rH°(970 K) = 0.45 ± 0.15 kcal/mol	Holm 1967
0.098	8164.1	SiO2 (cr, cristobalite) → SiO2 (vitr)	Δ_rH°(970 K) = 0.95 ± 0.15 (×1.354) kcal/mol	Holm 1967
0.014	8161.4	SiO2 (cr, quartz) → SiO2 (cr, cristobalite)	Δ_rH°(298.15 K) = 0.93 ± 0.52 kcal/mol	Humphrey 1952, Humphrey 1952a
0.002	8167.1	SiO2 (cr, cristobalite) → SiO2 (g)	Δ_rG°(1850 K) = 261.4 ± 10.9 (×4) kJ/mol	Porter 1955, 3rd Law
0.000	8175.2	SiO2 (cr, cristobalite) → SiO (g) + 1/2 O2 (g)	Δ_rG°(1956 K) = 317 ± 20 kJ/mol	Shchedrin 1977, 3rd Law, Gurvich TPIS
0.000	8175.1	SiO2 (cr, cristobalite) → SiO (g) + 1/2 O2 (g)	Δ_rG°(1850 K) = 260.5 ± 70 (×1.067) kJ/mol	Porter 1955, 3rd Law, Gurvich TPIS

References

1		B. Ruscic, R. E. Pinzon, M. L. Morton, G. von Laszewski, S. Bittner, S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner, Introduction to Active Thermochemical Tables: Several "Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 108, 9979-9997 (2004) [DOI: 10.1021/jp047912y]
2		B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, and A. F. Wagner, Active Thermochemical Tables: Thermochemistry for the 21^st Century. J. Phys. Conf. Ser. 16, 561-570 (2005) [DOI: 10.1088/1742-6596/16/1/078]
3		B. Ruscic and D. H. Bross, Active Thermochemical Tables (ATcT) values based on ver. 1.148 of the Thermochemical Network (2023); available at ATcT.anl.gov
4		T. L. Nguyen, J. Peeters, J.-F. Müller, A. Perera, D. H. Bross, B. Ruscic, and J. F. Stanton, Methanediol from Cloud-Processed Formaldehyde is Only a Minor Source of Atmospheric Formic Acid Natl. Acad. Sci. 120, e2304650120/1-8 (2023) [DOI: 10.1073/pnas.2304650120]
5		B. Ruscic, Uncertainty Quantification in Thermochemistry, Benchmarking Electronic Structure Computations, and Active Thermochemical Tables. Int. J. Quantum Chem. 114, 1097-1101 (2014) [DOI: 10.1002/qua.24605]
6		B. Ruscic and D. H. Bross, Thermochemistry Computer Aided Chem. Eng. 45, 3-114 (2019) [DOI: 10.1016/B978-0-444-64087-1.00001-2]

Formula

The aggregate state is given in parentheses following the formula, such as: g - gas-phase, cr - crystal, l - liquid, etc.

Uncertainties

The listed uncertainties correspond to estimated 95% confidence limits, as customary in thermochemistry (see, for example, Ruscic [5] and Ruscic and Bross[6]).
Note that an uncertainty of ± 0.000 kJ/mol indicates that the estimated uncertainty is < ± 0.000₅ kJ/mol.

Website Functionality Credits

The reorganization of the website was developed and implemented by David H. Bross (ANL).
The find function is based on the complete Species Dictionary entries for the appropriate version of the ATcT TN.
The molecule images are rendered by Indigo-depict.
The XYZ renderings are based on Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/.

Acknowledgement

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Contract No. DE-AC02-06CH11357.