Mixing is a pre-requisite for combustion. Mixing (i. decreasing bulk differences),is a natural process (i. it does not require an energy expenditure), so that, if fuel andoxidizer gases are brought to contact and enough time allowed, a perfect mixing wouldtake place in their energy level (temperature), relative speeds and chemical composition(with the natural stratification in the presence of gravity or another force field). But mixingis a slow physical process if not forced by convection (large-scale transport) and turbulence(large-scale to small-scale transport). Turbulent mixing is the rule in all practical fluidflows at scales larger than the millimeter, from the piping of water, fuels, gases..., to thewakes behind vehicles of any sort, to all atmosphere, ocean and stellar motions (there aresome exceptions, as the laminar diffusing contrails left by jet aircraft).
The fidelity of combustion simulations is strongly dependent on the accuracy of the underlying thermochemical properties for the core combustion species that arise as intermediates and products in the chemical conversion of most fuels. High level theoretical evaluations are coupled with a wide-ranging implementation of the Active Thermochemical Tables (ATcT) approach to obtain well-validated high fidelity predictions for the 0 K heat of formation for a large set of core combustion species. In particular, high level ab initio electronic structure based predictions are obtained for a set of 348 C, N, O, and H containing species, which corresponds to essentially all core combustion species with 34 or fewer electrons. The theoretical analyses incorporate various high level corrections to base CCSD(T)/cc-pVnZ analyses (n = T or Q) using H 2 , CH 4 , H 2 O, and NH 3 as references. Corrections for the complete-basis-set limit, higher-order excitations, anharmonic zero-point energy, core-valence, relativistic, and diagonal Born-Oppenheimer effects are ordered in decreasing importance. Independent ATcT values are presented for a subset of 150 species. The accuracy of the theoretical predictions is explored through (i) examination of the magnitude of the various corrections, (ii) comparisons with other high level calculations, and (iii) through comparison with the ATcT values. The estimated 2σ uncertainties of the three methods devised here, ANL0, ANL0-F12, and ANL1, are in the range of 1.0-1.5 kJ/mol for single-reference and moderately multireference species, for which the calculated higher order excitations are 5 kJ/mol or less. In addition to providing valuable references for combustion simulations, the subsequent inclusion of the current theoretical results into the ATcT thermochemical network is expected to significantly improve the thermochemical knowledge base for less-well studied species. 1e1e36bf2d