Modeling Nitrogen Species as Pollutants: Thermochemical Influences

Abstract

In order to simulate emissions of nitrogen-containing compounds in practical combustion environments, it is necessary to have accurate values for their thermochemical parameters, as well as accurate kinetic values to describe the rates of their formation and decomposition. Significant disparity is observed in the literature for the former, and we therefore present herein high-accuracy ab initio gas-phase thermochemistry for 60 nitrogenous compounds, many of which are important in the formation and consumption chemistry of NO x species. Several quantum-chemical composite methods (CBS-APNO, G3, and G4) were utilised in order to derive enthalpies of formation via the atomisation method. Entropies and heat capacities were calculated from traditional statistical thermodynamics, with oscillators treated as anharmonic based on ro-vibrational property analyses carried out at the B3LYP/cc-pVTZ level of theory. The use of quantum chemical methods, along with the treatments of anharmonicities and hindered rotors, ensures accurate enthalpy of formation, entropy, and heat capacity values across a temperature range of 298.15-3000 K. The implications of these results for atmospheric and combustion modelling are discussed. TOC graphic2

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