Active Thermochemical Tables: Thermochemistry for the 21st Century

Branko Ruscic (a), Reinhardt E. Pinzon (a), Gregor von Laszewski (b), Deepti Kodeboyina (b), Alexander Burcat (a,c), David Leahy (d), David Montoya (e), and Albert F. Wagner (a)
(a&b) Argonne National Laboratory
(c) Israel Institute of Technology
(d) Sandia National Laboratories, Livermore
(e) Los Alamos National Laboratory

Active Thermochemical Tables (ATcT) are a great example of a significant breakthrough in chemistry science that is directly enabled by the SciDAC initiative. ATcT is a new paradigm of how to obtain accurate, reliable, and internally consistent thermochemistry and overcome the limitations that are deeply engrained in the traditional approach to thermochemistry. The availability of high-quality consistent thermochemical values is central to chemistry and critical in many areas, such as development of sophisticated high-fidelity electronic structure computational treatments or development of realistic and predictive models of complex chemical environments such as combustion or the atmosphere. As opposed to the conventional sequential evolution of thermochemical values for the chemical species of interest, ATcT utilizes the Thermochemical Network (TN) approach. This approach explicitly exposes the inherent intricate interdependencies normally ignored by the conventional treatment, and allows, inter alia, a statistical analysis of the individual measurements that define the TN. The end result is the extraction of the best available thermochemistry, based on optimal use of all the knowledge that is available, hence making conventional tabulations of thermochemical values obsolete. Moreover, ATcT offer a number of additional features that are neither present nor possible in the traditional approach. With ATcT, new knowledge can be painlessly propagated through all affected thermochemical values. ATcT also allows hypothesis testing and evaluation, as well as discovery of weak links in the TN. The latter provides pointers to new experimental or theoretical determinations that will most efficiently improve the underlying thermochemical body of knowledge. The power of the ATcT approach is illustrated by providing significantly improved thermochemistry for several “key” thermochemical species (which are notorious for being next to impossible to improve on), together with illustration of how the ATcT paradigm impacts other recent developments in chemistry, such as experimental chemical kinetics and development of very-high-accuracy quantum-mechanical computations. This work was supported by the U.S. Department of Energy, Division of Chemical Sciences, Geosciences and Biosciences of the Office of Basic Energy Sciences, and by the Mathematical, Information, and Computational Science Division of the Office of Advanced Scientific Computing Research, under Contract No. W-31-109-ENG-38. Computer science aspects of this work are an intimate part of the Collaboratory for Multi-Scale Chemical Science (CMCS), sponsored by the U.S. Department of Energy’s Division of Mathematical, Information, and Computational Sciences of the Office of Advanced Scientific Computing Research, and has benefited from the support and effort of the numerous past and present CMCS team members Portions of this research are also related to the effort of a Task Group of the International Union of Pure and Applied Chemistry (2003-024-1-100).