Clarifying NH2 + O(3P) Reaction Dynamics: A Full-Dimensional MRCI, Machine-Learned PES Unravels High-Temperature Kinetics

Abstract

The NH2 + O reaction represents a critical oxidation pathway in ammonia and hydrazine combustion, yet significant discrepancies persist in reported kinetics. Here, we generate a full-dimensional ground-state potential energy surface (PES) for NH2O using high-level internally contracted multi-reference configuration interaction (ic-MRCI) calculations and the permutation invariant polynomial-neural network (PIP-NN) method. The PES encompasses all energetically accessible channels, including HNO + H, NH + OH, NO + H2, and HON + H. Quasi-classical trajectory calculations on this surface yield thermal rate coefficients and branching ratios over a wide temperature range, particularly extending into the high-temperature regime relevant to combustion. The results provide accurate first principles kinetic data essential for refining combustion models of nitrogen containing fuels.