A global fundamental invariant neural networks potential energy surface and dynamics study of the hydroxyl radical and ammonia reaction

Abstract

The reaction between hydroxyl radical (OH) and ammonia (NH3) holds significant importance in both combustion and atmospheric chemistry, and serves as a typical six-atom reaction system involving two heavy atoms. In this work, a global ground electronic state potential energy surface (PES) for the OH + NH3 reaction was constructed using the fundamental invariant neural network (FI-NN) fitting method, based on 77330 ab initio energy points calculated at the AE-UCCSD(T)-F12a/AVTZ theoretical level. The overall root-mean-square error (RMSE) is 10.55 meV. The PES accurately describes not only the hydrogen abstraction channel, but also the NH2OH formation channel. Based on the new PES, integral cross sections (ICSs) for both channels were calculated, and the product state distributions were analyzed, using quasi-classical trajectory (QCT) method. The rate coefficients of the hydrogen abstraction channel were also calculated over the temperature range of 300 K to 2000 K.