Accurate ab initio‐based double many‐body expansion adiabatic potential energy surface for the 22 A′ state of NH2 by extrapolation to the complete basis set limit

Abstract

AbstractAn accurate single‐sheeted double many‐body expansion potential energy surface (PES) is reported for the title system, which is suitable for dynamics and kinetics studies of the reactions N(2D) + H2(X1 Σ) ⇋ NH(b1 Σ+) + H(2S) and their isotopomeric variants. It is obtained using the aug‐cc‐pVTZ and aug‐cc‐pVQZ basis sets with extrapolation of the electron correlation energy to the complete basis set limit, plus extrapolation to the complete basis set limit of the complete‐active‐space self‐consistent field energy. A switching function formalism has been used to ensure the correct behavior at the NH(A3 Π) + H(2S) and NH(b1 Σ+) + H(2S) dissociation limits. The topographical features of the new global PES are examined in detail, and found to be in general good agreement with those calculated directly from the raw ab initio energies, as well as previous calculations from the literature. © 2012 Wiley Periodicals, Inc.