Modeling Nitrogen Species as Pollutants: Thermochemical Influences

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 NOx species. Several quantum-chemical composite methods (CBS-APNO,
G3, and G4) were utilized to derive enthalpies of formation via the
atomization 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 the temperature range 298.15–3000 K.
The implications of these results for atmospheric and combustion modeling
are discussed.