An accurate NH2(X2A′′) CHIPR potential energy surface via extrapolation to the complete basis set limit and dynamics of the N(2D) + H2(X1Σ +g) reaction

Abstract

The amidogen radical (NH₂) and its associated N(²D) + H₂(X¹Σ⁺_g) → H(²S) + NH(X³Σ⁻) reaction have great significance in interstellar chemistry and the accurate potential energy surface (PES) is the basis for studying them. We report a new and accurate PES for the ground state NH₂(X²A′′) using the combined-hyperbolic-inverse-power-representation methodology based on 7970 ab initio energy points computed at the Davidson-corrected internally contracted multireference configuration interaction level of theory. Both aug-cc-pVTZ and aug-cc-pVQZ basis sets have been employed to extrapolate the energies to the complete basis set limit. The analytical PES reproduces well with the ab initio energy points with a root mean square deviation of 55.7 cm⁻¹. The topographical features of the analytical PES are examined in detail and agree well with the previous theoretical results. The integral cross sections and rate constants of the N(²D) + H₂(X¹Σ⁺_g) → H(²S) + NH(X³Σ⁻) reaction are obtained using the quasi-classical trajectory method and the time-dependent wave packet method and then compared with the available theoretical and experimental values.