Thermochemical activation

The choice of a given database as source of auxiliary values may not be straightforward, even for a thermochemist. Consistency is a very important criterion, but factors such as the publication year, the assignment of an uncertainty to each value, and even the scientific reputation of the authors or the origin of the database matter. For instance, it would not be sensible to use the old NBS Circular 500 [22] when the NBS Tables of Chemical Thermodynamic Properties [17], published in 1982, is available. If we need a value for the standard enthalpy of formation of an organic compound, such as ethanol, we will probably prefer Pedley s Thermodynamic Data and Structures of Organic Compounds [15], published in 1994, which reports the error bars. Finally, if we are looking for the standard enthalpy of formation of any particular substance, we should first check whether it is included in CODATA Key Values for Thermodynamics [16] or in the very recent Active Thermochemical Tables [23,24],... 

K. A. Amin, M. Minkoff, A. F. Wagner. Introduction to Active Thermochemical Tables Several Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 2004, 108, 9979-9997. 

B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, A. F. Wagner. Active Thermochemical Tables Thermochemistry for the 21st Century. J. Physics Conference Series 2005,16, 561-570. 

The Active Thermochemical Tables (ATcT) are the result of an effort to derive accurate, reliable, and internally consistent thermochemical values based on a thermochemical network approach. They contain data for over 350 compounds. Recommended values for key compounds such as CC>2(g), H20(g), and CH4(g) are slightly different from those given by CODATA. 

A. Burcat, B. Ruscic, Ideal Gas Thermochemical Database with updates from Active Thermochemical Tables, http //garfield.chem.elte.hu/Burcat/burcat.html, July 5,2007. 

In contrast to the stable hydrocarbons, where the standard enthalpy of formation is based on one or another of the direct calorimetrical methods, values for radicals come from all sorts of very difficult measurements ranging from photoionization mass spectroscopy to measurements of reaction rates. It is no surprise that the results are more contentious and less accurate. In Table 1.3, the uncertainty ranges can be seen to be typically an order of magnitude greater than those for stable hydrocarbon values except where the Active Thermochemical Tables can help. 

A. Burcat and B. Ruscic,Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion with Updates from Active Thermochemical Tables, ANL-Report-05/20 and TAE Report 960 (2005) (now authored by E. Goos, B. Ruscic and A. Burcat, data available on request from Elke.Goos dlr.de). 

Ruscic B (2014) Active thermochemical tables, version 1.112, Argonne national laboratory, Argonne, IL. http //atct.anl.gov... 

B. Ruscic, Active Thermochemical Tables, 2005 Yearbook of Science and Technology (annual update to McGraw-Hill Encyclopedia of Science and Technology), University Science Books, McGraw-Hill, New York, 2004. 

B. Ruscic, unpublished results obtained from Active Thermochemical Tables (ATcT) ver. 1.36 using the Core (Argonne) Thermochemical Network ver. 1.070, 2008. 

A. Burcat and B. Ruscic. Third Millennium Ideal Gas and Condensed Phase Thermochemical Database for Combustion with Updates from Active Thermochemical Tables. Report TAE960, 2005. 

Acknowledgements I thank Dr. Stephen Klippenstein for helpful discussion of uncertainties in transition state energies in electronic structure calculations and Dr. Branko Ruscic for the provision of recent data for the Active Thermochemical Tables (ATcT). 

Ruscic B, Pinzon RE, von Laszewski G, Kodeboyina D, Bnrcat A, Leahy D, Montoya D, Wagner AF (2005) Active thermochemical tables thermochemistry for the 21st century. In Conference on scientific discovery through advanced computing (SciDAC 2005), vol 16. San Francisco, pp 561-570... 

Ruscic, B., Active Thermochemical Table, http //atct.anl.gov/index. html, Dec. 16, 2010. 

Burcat, A. Thermochemical Data for Combustion Calculations. Springer, New York (1984) Burcat, A. Thermodyanamic database. http //garfield.chem.elte.hu/Burcat/burcat.html Burcat, A., Ruscic, B. Third Millenium ideal gas and condensed phase thermochemical database for combustion with updates from Active Thermochemical Tables. Argonne National Laboratory report ANL-05/20 (2005)... 

Note, that typical thermodynamic databases contain the uncertainties of the enthalpies of formation of the species separately and do not provide information about correlation of these uncertainties. The Active Thermochemical Table (ATcT) approach (Ruscic et al. 2004,2005,2006,2014 Ruscic Stevens et al. 2010 Ruscic 2013,2014) takes into account that many measurements contain information for the thermodynamic data of several species together, and therefore the determination of the thermodynamic data from all available experimental measurements and theoretical calculations has to occur in a single step. This approach makes the... 

Ruscic, B. Active thermochemical tables water and water dimer. J. Phys. Chem. A 117, 11940-11953(2013)... 

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