Automated Mechanism Generation: From Symbolic Calculation to Complex Chemistry ARTUR RATKIEWICZ, 1 THANH N. TRUONG 2 1 Chemistry Institute, University at Bialystok, Hurtowa 1 15-399 Bialystok, Poland 2 Department of Chemistry, Henry Eyring Center for Theoretical Chemistry, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112, USA Received 1 May 2005; accepted 2 June 2005 Published online 12 August 2005 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/qua.20748 ABSTRACT: Different aspects of the symbolic algebra computations for generating elementary reactions of complex systems are reviewed. Such calculations are the heart of each automated mechanism generator system and are employed extensively in different stages of mechanism generation. The range of symbolic calculation topics and basic ideas of these implementations, together with some specific examples, are given. Particular attention is devoted to the transition between the symbolic calculation and the real complex chemistry. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem 106: 244 –255, 2006 Key words: symbolic algebra calculation; automated mechanism generation; reaction pattern; graph theory; on-the-fly kinetics 1. Introduction B ridging the gap between the micromecha- nism and the macrophenomena, in time and length scales, has become one of the major thrusts in science and engineering in the new millennium. One such challenge is to perform simulations of a combustion engine (length scale of meters and time scale of minutes to hours) with a detailed reaction mechanism consisting of all important elementary reactions (length scale of nanometer and time scale of femtosecond) to monitor concentration profiles of both major and minor products. In many chem- ical processes, minor products are often hazardous environmental contaminants. Thus, the ability to perform such a simulation will have significant im- pacts on many industries as well as on our environ- ment. However, to achieve this goal, we must be able to develop detailed mechanisms of complex reactions. Developing such mechanisms is at the heart of chemistry, since it allows chemists to make verifiable predictions for systems of real interest based on theories and/or measurements made in highly simplified laboratory conditions. The prob- Correspondence to: T. N. Truong; e-mail: truong@ chemistry.hec.utah.edu International Journal of Quantum Chemistry, Vol 106, 244 –255 (2006) © 2005 Wiley Periodicals, Inc.