News:
Computational Prediction of Kinetic Rate Constants
A core component of aerospace manufacturing is based on cutting-edge technological applications of material design. For example, the metal parts in aircraft engines are often protected by ceramic thermal barrier coatings to shield them from the extreme combustion environment. Materials designed for extreme environments are also found on the outer skin of aerospace vehicles, the leading edges of wing surfaces, and the walls of engine inlets. Chemical kinetics models are vital for interpreting experimental measurements and predicting the behavior of these complex systems. For many applications, reaction rates for most, if not all, of the required chemical processes are not known. Modern computational chemistry methods have proven to be invaluable for the accurate prediction of reaction rates for kinetics models, but the techniques are highly specialized. The calculation of rate constants from "first principles" still necessitates the concurrent use of a number of different codes for predicting molecular electronic structure, chemical dynamics, and reaction rate constants. These codes are readily available but lack a unified runtime environment and require expert user intervention during intermediate steps. Spectral Sciences, Inc. (SSI) and Battelle Memorial Institute, Pacific Northwest Division are enhancing the Extensible Computational Chemistry Environment (Ecce, pronounced "etch-ay") [http://ecce.emsl.pnl.gov/], a state-of-the-art graphical user interface, to incorporate reaction rate constant calculations; thus creating the first unified computational kinetics package of its kind (Figure 1). The objective of this STTR program is to extend Ecce, enabling it to seamlessly perform calculations based on the electronic structure code NWChem [http://www.emsl.pnl.gov/docs/nwchem/nwchem.html], the dynamics code VENUS [http://monte.chem.ttu.edu/group/venus.html], and the transition state theory code POLYRATE [http://comp.chem.umn.edu/polyrate/]. Together, this set of codes will allow the non-expert to calculate reaction rate constants from high-level quantum calculations within a single environment, while providing a realistic prediction of the inherent errors associated with the calculation. Although great advances in the separate aspects of computational modeling have been achieved, we are not aware of any package that consolidates these approaches into a unified, user-friendly environment as we propose.
Figure 1. The current and proposed computational kinetics paradigms.
In the current paradigm an expert user is required to intervene at intermediate stages of the calculation. In the proposed paradigm the entire calculation proceeds through one centralized interface.